Watanabe Masao
Faculty of Engineering Mechanical and Aerospace Engineering Thermal and Fluid Systems | Professor |
Last Updated :2025/02/13
■Researcher basic information
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Research Keyword
- 分子気体力学
- extra cellular matrix
- 気液界面
- 混相流
- 気液二相流
- Surface Tension
- 軟骨細胞
- transport phenolnena
- visualization
- 移流
- high speed digital video
- 再生医療
- CFD
- Computational fluid dynamics
- 自由界面
- Phase contrast
- Bubble Cloud
- PIV法
- cell
- Magnetic Resonant Angiography
- bubble
- モデリング
- 拡散
- Inverse poblem
- Inverse problem
- Bubble generation
- PIV
- bovine Articular Cartilage
- Finite Element Method
Research Field
Educational Organization
- Bachelor's degree program, School of Engineering
- Master's degree program, Graduate School of Engineering
- Doctoral (PhD) degree program, Graduate School of Engineering
■Career
Career
■Research activity information
Awards
- Oct. 2017, 一般社団法人日本機械学会, 日本機械学会流体工学部門貢献表彰
渡部 正夫 - Oct. 2014, 日本学術振興会, 科研費審査員表彰
渡部 正夫 - Aug. 2013, 日本混相流学会, 2012年度日本混相流学会 学会賞・論文賞
気泡後部トロイダル渦の抗力への寄与
城田農;佐藤文香;真田俊之;渡部正夫, Japan society, Japan - Mar. 2012, The Japan Society of Mechanical Engineers, JSME Medal for Outstanding Paper
Unified Theory Based on Parameter Scaling for Derivation of Nonlinear Wave Equations in Bubbly Liquids
Tetsuya KANAGAWA;Takeru YANO;Masao WATANABE;Shigeo FUJIKAWA
Papers
- Particle size distribution effects on the light scattering properties in non-diluted colloidal suspensions: A numerical study
Hiroyuki Fujii, Hyeonwoo Na, Jungyun Yi, Kazumichi Kobayashi, Masao Watanabe
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 135208, 135208, Elsevier BV, Aug. 2024
Scientific journal - Interference effects on light scattering properties of dense colloidal suspensions: a short review
Hiroyuki Fujii, Hyeonwoo Na, Koyata Nishikawa, Kazumichi Kobayashi, Masao Watanabe
Optical Review, 31, 3, 299, 308, Springer Science and Business Media LLC, 22 May 2024
Scientific journal, Abstract
Near-infrared spectroscopy and imaging using scattered light potentially evaluate the structural properties of the medium, like the average particle size, based on a relation between its structure and light scattering. A qualitative understanding of light scattering is crucial for developing optical imaging techniques. The scattering properties of dense colloidal suspensions have been extensively investigated using the electromagnetic theory (EMT). The colloidal suspensions are widely used in liquid tissue phantoms for optical imaging techniques and are encountered in various fields, such as the food and chemical industries. The interference between electric fields scattered by colloidal particles significantly influences the scattering properties, so-called the interference effects. Despite many efforts since the 1980s, a complete understanding of the interference effects has still not been achieved. The main reason is the complicated dependence of the interference on the optical wavelength, particle size, and so on. This paper briefly reviews numerical and theoretical studies of the interference effect based on the dependent scattering theory, one of the EMTs, and model equations. - Couette flow at high Knudsen number between wall and liquid boundaries
Kazumichi Kobayashi, Kota Aoki, Hirofumi Tabe, Hiroyuki Fujii, Toshiki Nara, Hideyoshi Takashima, Nobuyuki Oshima, Masao Watanabe
Physics of Fluids, 35, 8, AIP Publishing, 01 Aug. 2023
Scientific journal, This paper presents molecular dynamics simulations of the Couette flow of a rarefied gas between the liquid and wall boundaries and, in particular, investigates the boundary conditions for the Boltzmann equation at the liquid interface. The simulation results for various Knudsen numbers show that the slip velocity decreases at the liquid boundary and increases at the smooth wall as the Knudsen number increases, indicating that the velocity profile of the rarefied Couette flow is asymmetric. One reason for this is backscattering, in which molecules are reflected in the opposite direction to the mainstream flow, owing to molecular-scale roughness at the liquid boundary. It has also been suggested that the backscattering effect decreases when the gas density increases. This can be understood using the local Knudsen numbers near the liquid boundary. - Numerical study of light scattering and propagation in soymilk: Effects of particle size distributions, concentrations, and medium sizes
Hiroyuki Fujii, Koyata Nishikawa, Hyeonwoo Na, Yuki Inoue, Kazumichi Kobayashi, Masao Watanabe
Infrared Physics & Technology, 132, 104753, 104753, Elsevier BV, Aug. 2023
Scientific journal - Vapor condensation induced by fast-moving liquid film in the presence of noncondensable gas molecules
Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
International Communications in Heat and Mass Transfer, 142, 106622, 106622, Elsevier BV, Mar. 2023
Scientific journal - Modeling photoacoustic pressure generation in colloidal suspensions at different volume fractions based on a multi-scale approach
Hiroyuki Fujii, Iori Terabayashi, Kazumichi Kobayashi, Masao Watanabe
Photoacoustics, 27, 100368, 100368, Elsevier BV, Sep. 2022
Scientific journal - Wetting failure in the early stage of water drop impact on a smooth solid surface
Ryunosuke Adachi, Kazumichi Kobayashi, Hiroyuki Fujii, Toshiyuki Sanada, Masao Watanabe
Physics of Fluids, 34, 6, 062116, 062116, AIP Publishing, Jun. 2022
Scientific journal, A water drop impacting a dry solid surface can eject a thin liquid sheet, which is forced to expand on the surface to wet the solid surface. Wetting failure, which produces defects in applications based on the impact of drops, including coating, cooling, cleaning, and printing, may occur with a sufficiently large liquid-sheet velocity. However, the exact onset of wetting failure when a drop impacts the surface has yet to be determined. Therefore, we examine the dependence of rim instability immediately after liquid-sheet ejection on the static contact angle of the solid surface at the instant of water drop impact. This study is the first attempt to solve this problem and is made possible only by using an ultra-high-speed camera. We revealed that wetting failure can occur by investigating the rim instability of the liquid sheet. - Molecular dynamics simulation of evaporation coefficient of vapor molecules during steady net evaporation in binary mixture system
Hirofumi Tabe, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
International Journal of Heat and Mass Transfer, 188, 122663, 122663, Elsevier BV, Jun. 2022
Scientific journal - Molecular dynamics study of evaporation induced by locally heated argon liquid
Hirofumi Tabe, Kiryu Hiramatsu, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe, Tsuyoshi Totani
Applied Thermal Engineering, 212, 118472, 118472, Elsevier BV, Apr. 2022
Scientific journal - Model equations of light scattering properties and a characteristic time of light propagation for polydisperse colloidal suspensions at different volume fractions
Hiroyuki Fujii, Moegi Ueno, Yuki Inoue, Toshiaki Aoki, Kazumichi Kobayashi, Masao Watanabe
Optics Express, 30, 3, 3538, 3538, The Optical Society, 31 Jan. 2022
Scientific journal - Numerical Study of Near-Infrared Light Propagation in Aqueous Alumina Suspensions Using the Steady-State Radiative Transfer Equation and Dependent Scattering Theory
Hiroyuki Fujii, Iori Terabayashi, Toshiaki Aoki, Yuki Inoue, Hyeonwoo Na, Kazumichi Kobayashi, Masao Watanabe
Applied Sciences, 12, 3, 1190, 1190, MDPI AG, 24 Jan. 2022
Scientific journal, Understanding light propagation in liquid phantoms, such as colloidal suspensions, involves fundamental research of near-infrared optical imaging and spectroscopy for biological tissues. Our objective is to numerically investigate light propagation in the alumina colloidal suspensions with the mean alumina particle diameter of 55 nm at the volume fraction range 1–20%. We calculated the light scattering properties using the dependent scattering theory (DST) on a length scale comparable to the optical wavelength. We calculated the steady-state radiative transfer and photon diffusion equations (RTE and PDE) using the DST results based on the finite difference method in a length scale of the mean free path. The DST calculations showed that the scattering and reduced scattering coefficients become more prominent at a higher volume fraction. The anisotropy factor is almost zero at all the volume fractions, meaning the scattering is isotropic. The comparative study of the RTE with the PDE showed that the diffusion approximation holds at the internal region with all the volume fractions and the boundary region with the volume fraction higher than 1%. Our findings suggest the usefulness of the PDE as a light propagation model for the alumina suspensions rather than the RTE, which provides accurate but complicated computation. - Mean-field kinetic theory analysis of vapor flow between evaporating and condensing interfaces in the presence of non-condensable gas molecules
Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
Physics of Fluids, 33, 12, 122017, 122017, AIP Publishing, Dec. 2021
Scientific journal - Numerical Modelling of Initial Photoacoustic Pressure in Colloidal Suspensions for Photoacoustic Imaging
Hiroyuki Fujii, Toshiaki Aoki, Yuki Inoue, Iori Terabayashi, Kazumichi Kobayashi, Masao Watanabe
Technical digest of 26th Microoptics Conference (MOC2021), PO-11, 164, 165, The Japan Society of Applied Physics, Sep. 2021, [Peer-reviewed]
English, International conference proceedings - Molecular dynamics study on characteristics of reflection and condensation molecules at vapor–liquid equilibrium state
Hirofumi Tabe, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
PLOS ONE, 16, 3, e0248660, e0248660, Public Library of Science (PLoS), 16 Mar. 2021, [Peer-reviewed], [Last author]
Scientific journal, The kinetic boundary condition (KBC) represents the evaporation or condensation of molecules at the vapor–liquid interface for molecular gas dynamics (MGD). When constructing the KBC, it is necessary to classify molecular motions into evaporation, condensation, and reflection in molecular-scale simulation methods. Recently, a method that involves setting the vapor boundary and liquid boundary has been used for classifying molecules. The position of the vapor boundary is related to the position where the KBC is applied in MGD analyses, whereas that of the liquid boundary has not been uniquely determined. Therefore, in this study, we conducted molecular dynamics simulations to discuss the position of the liquid boundary for the construction of KBCs. We obtained some variables that characterize molecular motions such as the positions that the molecules reached and the time they stayed in the vicinity of the interface. Based on the characteristics of the molecules found from these variables, we investigated the valid position of the liquid boundary. We also conducted an investigation on the relationship between the condensation coefficient and the molecular incident velocity from the vapor phase to the liquid phase. The dependence of the condensation coefficient on the incident velocity of molecules was confirmed, and the value of the condensation coefficient becomes small in the low-incident-velocity range. Furthermore, we found that the condensation coefficient in the non-equilibrium state shows almost the same value as that in the equilibrium state, although the corresponding velocity distribution functions of the incident velocity significantly differ from each other. - A comparative study of the delta-Eddington and Galerkin quadrature methods for highly forward scattering of photons in random media
Hiroyuki Fujii, Go Chiba, Yukio Yamada, Yoko Hoshi, Kazumichi Kobayashi, Masao Watanabe
Journal of Computational Physics, 423, 109825, 109825, Elsevier BV, Sep. 2020, [Peer-reviewed], [Last author]
English, Scientific journal, A versatile and accurate treatment for the highly forward-peaked phase function in the three-dimensional (3D) radiative transfer equation (RTE) based on the discrete ordinates method (DOM) is crucial for biomedical optics. Our first objective was to compare the delta-Eddington (dE) and Galerkin quadrature (GQ) methods. The dE method decomposes the phase function into a purely forward-peaked component and the other component, and expands the other component by Legendre polynomials as well as the finite order Legendre expansion (FL) method does. The GQ method conducts the weighting procedure in addition to the Legendre expansion. Although it was reported that both methods can provide the accurate results for calculations of the RTE, the versatility of both methods is still unclear. The second objective was to examine a possibility of a conjunction of the GQ method with the dE method, called as the GQ-dE method, which has the advantages of both methods. We examined numerical errors in the moment conditions of the phase function using the FL, dE, GQ and GQ-dE methods at various types and orders of the quadrature sets, mainly in the region of the errors induced by the angular discretization using the DOM. The errors were reduced by the dE method from those by the FL method, however the error reduction depended on the types and orders of the quadrature sets. Meanwhile, the errors were significantly reduced by the GQ and GQ-dE methods, regardless of the quadrature sets. We also verified the numerical calculations of the time-dependent 3D RTE by the analytical solution of the RTE for homogeneous media in the region of the scattering length scale, where the highly forward-peaked phase function strongly influences the RTE-results. The errors in the RTE-results were similar to those in the moment conditions. Our results suggest the higher versatility and accuracy of the GQ and GQ-dE methods than those of the FL and dE methods. (C) 2020 Elsevier Inc. All rights reserved. - Photon transport model for dense polydisperse colloidal suspensions using the radiative transfer equation combined with the dependent scattering theory
Hiroyuki Fujii, Leung Tsang, Jiyue Zhu, Koki Nomura, Kazumichi Kobayashi, Masao Watanabe
Optics Express, The Optical Society, 10 Jul. 2020, [Peer-reviewed], [Last author]
Scientific journal - Evaporation coefficient and condensation coefficient of vapor under high gas pressure conditions
Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
Scientific Reports, 10, 8143, 18 May 2020, [Peer-reviewed], [Last author]
English, Scientific journal - Levitation mechanism of impacting nanodroplet on heated wall
Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
International Journal of Thermal Sciences, 150, 106203, 106203, Elsevier BV, Apr. 2020, [Peer-reviewed]
Scientific journal - Enhancement of Gas Discharge from a Closed End Hole by Using Acoustic Wave Irradiation
Yuki FURUYA, Yuki MIZUSHIMA, Masao WATANABE, Toshiyuki SANADA
JAPANESE JOURNAL OF MULTIPHASE FLOW, 34, 1, 111, 117, The Japanese Society for Multiphase Flow, 15 Mar. 2020
Scientific journal - Analysis of interference effects on light scattering in colloidal suspensions
Koki Nomura, Hiroyuki Fujii, Kazumichi Kobayashi, Masao Watanabe, Goro Nishimura
Proceeding of the 7th Asian NIR symposium (ANS2020), 2020, AFI-0006, 12, 13, Feb. 2020, [Peer-reviewed]
English, International conference proceedings - Finite element investigation of light propagationin the human neck using the time-dependent radiative transfer theory
Shigeki Endo, Hiroyuki Fujii, Kazumichi Kobayashi, Masao Watanabe
Proceeding of the 7th Asian NIR symposium (ANS2020), 2020, NRT-0008, 60, 61, Feb. 2020, [Peer-reviewed]
English, International conference proceedings - Numerical study on light propagation in a white bread loaf
Hiroyuki Fujii, Goro Nishimura, Shigeki Endo, Koki Nomura, Kazumichi Kobayashi, Masao Watanabe
Proceeding of the 7th Asian NIR symposium (ANS2020), 2020, AFI-0007, 14, 15, Feb. 2020, [Peer-reviewed], [International Magazine]
English, International conference proceedings - Special Issue of the AJK2019, ASME-JSME-KSME Joint Fluids Engineering Conference 2019 Preface
Shinnosuke Obi, Koji Fukagata, Masaharu Kameda, Chisachi Kato, Yohei Morinishi, Yuichi Murai, Satoshi Watanabe, Masao Watanabe
JOURNAL OF FLUID SCIENCE AND TECHNOLOGY, 15, 2, JAPAN SOC MECHANICAL ENGINEERS, 2020
English - Hidden prompt splashing by corona splashing at drop impact on a smooth dry surface
Taku Ashida, Masao Watanabe, Kazumichi Kobayashi, Hiroyuki Fujii, Toshiyuki Sanada
Physical Review Fluids, 5, 1, 011601, American Physical Society (APS), Jan. 2020, [Peer-reviewed], [Corresponding author]
English, Scientific journal - Characteristic Length and Time Scales of the Highly Forward Scattering of Photons in Random Media
Hiroyuki Fujii, Moegi Ueno, Kazumichi Kobayashi, Masao Watanabe
Applied Sciences, 10, 1, 93, Dec. 2019, [Peer-reviewed]
English, Scientific journal - Numerical treatment of highly forward scattering on radiative transfer using the delta-M approximation and Galerkin quadrature method
Hiroyuki Fujii, Go Chiba, Yukio Yamada, Yoko Hoshi, Kazumichi Kobayashi, Masao Watanabe
Proceedings of the 9th International Symposium on Radiative Transfer, RAD-19, SM05, 261, 268, Sep. 2019, [Peer-reviewed]
English, International conference proceedings - Numerical errors of light propagation in the two-dimensional human neck model using the time-dependent radiative transfer equation with renormalized phase functions
Hiroyuki Fujii, Yamada Yukio, Hoshi Yoko, Kobayashi Kazumichi, Watanabe Masao
AIP Conference Proceedings (ICNAAM2018), 2116, 450037, 1, 4, Jul. 2019, [Peer-reviewed]
English, International conference proceedings - Finite element investigation of a void region on light propagation in scattering media using the radiative transfer equation
Kosuke Tabayashi, Hiroyuki Fujii, Kazumichi Kobayashi, Masao Watanabe
AIP Conference Proceedings (ICNAAM2018), 2116, 450052, 1, 4, Jul. 2019, [Peer-reviewed]
English, International conference proceedings - Influence of a small amount of noncondensable gas on shock wave generation inside a collapsing vapor bubble
Kyohei Yamamoto, Kazumichi Kobayashi, Masao Watanabe, Hiroyuki Fujii, Misaki Kon, Hiroyuki Takahira
Physical Review Fluids, 4, 6, American Physical Society, 11 Jun. 2019
English, Scientific journal, In this paper, the influence of a small amount of noncondensable gas on shock wave generation inside a collapsing vapor bubble is examined by combining numerical analysis of a bubble dynamics equation and of the Boltzmann equation for gas flow inside a bubble. We show the importance of the high Knudsen number in the flow, i.e., the nonequilibrium gas flow, to the temperature field inside the collapsing bubble. We also show that the maximum mean Knudsen number inside the collapsing bubble can be evaluated from the initial Knudsen number and the initial number density ratio of noncondensable gas and vapor molecules. As a result, we conclude that a small amount of noncondensable gas strongly affects the temperature field inside the collapsing bubble, preventing shock wave generation inside the bubble in the final stage of collapse. - Light propagation models of the human neck for photoacoustic imaging of thyroid cancer
Kosuke Tabayashi, Hiroyuki Fujii, Shinpei Okawa, Kazumichi Kobayashi, Yukio Yamada, Yoko Hoshi, Masao Watanabe
CMBE Proceedings (6th International Conference on Computational & Mathematical Biomedical Engineering), A5, 161, 164, May 2019, [Peer-reviewed]
English, International conference proceedings - Correction to: Influence of liquid–solid intermolecular force on levitation of impacting nanodroplet (Heat and Mass Transfer, (2019), 55, 4, (993-1003), 10.1007/s00231-018-2474-4)
Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
Heat and Mass Transfer/Waerme- und Stoffuebertragung, 55, 4, 1005, Springer Verlag, 11 Apr. 2019
English, Scientific journal, During typesetting of the article, Figure 7 was changed. The correct image is shown below. - Influence of liquid–solid intermolecular force on levitation of impacting nanodroplet
Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
Heat and Mass Transfer, 55, 4, 993, 1003, Springer Science and Business Media LLC, Apr. 2019, [Peer-reviewed]
English, Scientific journal - A model for a gas column oscillation inside a hole by irradiating an acoustic wave
Yuki Furuya, Toshiyuki Sanada, Masao Watanabe
ASME-JSME-KSME 2019 8th Joint Fluids Engineering Conference, AJKFluids 2019, 5, American Society of Mechanical Engineers (ASME), 2019
English, International conference proceedings, Wet cleaning methods using fluid are widely applied in many industrial fields. For a cleaning inside closed-end holes, it is first necessary to fill the holes to be cleaned with the liquid. However, in structures with small holes, it is difficult to discharge inside the gas due to surface tension. In our early studies, we have found that the discharging a gas inside a closed-end hole was promoted by an impingement of droplet train. And the pressure fluctuation near the gas-liquid interface due to droplet impingement was important. In this study, we attempted the gas discharge from closed-end holes due to acoustic wave irradiation. First, we theoretically estimated the oscillation of the gas column inside the hole during acoustic wave irradiation. We modeled the natural frequency of the gas column using a spring-mass system. Then we experimentally measured the fluctuation of the gas-liquid interface for the evaluation of the model. In addition, we compared the gas discharge ratio with different frequency and pressure level. The fluctuation of gas-liquid interface and discharging the gas were observed with a high-speed video camera. As results, the natural frequencies of a gas column were depending on the length of the gas column and the diameter of the hole. From the experiments, we confirmed that the acoustic wave certainly propagated into the hole, and the frequency of the irradiated acoustic wave and the experimentally obtained natural frequency were in good agreement except for extremely low gas discharge ratio condition. Moreover, we observed gas discharge process and found that the high gas discharge ratio were achieved using the acoustic wave close to natural frequency. From these results, we concluded that the assumption based on a spring-mass system is valid. - Molecular Dynamics Study on Influence of Liquid-solid Intermolecular Force on Levitating Mechanism of Impacting Nanodroplet on Heated Wall
Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
Surface Wettability Effects on Phase Change Phenomena(SWEP), 2019, [Peer-reviewed] - Molecular gas dynamics analysis on condensation coefficient of vapour during gas-vapour bubble collapse
Kazumichi Kobayashi, Takahiro Nagayama, Masao Watanabe, Hiroyuki Fujii, Misaki Kon
Journal of Fluid Mechanics, 856, 1045, 1063, Dec. 2018, [Peer-reviewed]
English, Scientific journal, This study investigates the influence of the condensation coefficient of vapour on the collapse of a bubble composed of condensable gas (vapour) and non-condensable gas (NC gas). We simulated vapour and NC gas flow inside a bubble based on the molecular gas dynamics analysis in order to replicate the phase change (viz., evaporation and condensation) precisely, by changing the initial number density ratio of the NC gas and vapour, the initial bubble radius and the value of the condensation coefficient. The results show that the motion of the bubble is unaffected by the value of the condensation coefficient when that value is larger than approximately 0.4. We also discuss NC gas drift at the bubble wall during the final stage of the bubble collapse and its influence on the condensation coefficient. We conclude that vapour molecules can behave as NC gas molecules when the bubble collapses, owing to the large concentration of NC gas molecules at the gas–liquid interface. That is, the condensation coefficient reaches almost zero when the bubble collapses violently. - Accurate and efficient computation of the 3D radiative transfer equation in highly forward-peaked scattering media using a renormalization approach
Hiroyuki Fujii, YukioYamad, Go Chiba, Yoko Hoshi, Kazumichi Kobayashi, Masao Watanabe
Journal of Computational Physics, 371, 591, 604, Dec. 2018, [Peer-reviewed]
English, Scientific journal - Pressure generated at the instant of impact between a liquid droplet and solid surface
Y. Tatekura, M. Watanabe, K. Kobayashi, T. Sanada
Royal Society Open Science, 5, 12, 181101, Dec. 2018, [Peer-reviewed], [Corresponding author]
English, Scientific journal - Observation of liquid infiltration process into closed-end holes by droplet train impingement
Toshiyuki SANADA, Yuki FURUYA, Shunsuke MURAKI, Masao WATANABE
Journal of Fluid Science and Technology, 13, 3, JFST0012, JFST0012, Japan Society of Mechanical Engineers, Oct. 2018, [Peer-reviewed]
English, Scientific journal - Light propagation model of titanium dioxide suspensions in water using the radiative transfer equation
Hiroyuki Fujii, Yukio Yamada, Yoko Hoshi, Shinpei Okawa, Kazumichi Kobayashi, Masao Watanabe
Reaction Kinetics, Mechanisms and Catalysis, 123, 2, 439, 453, Springer Netherlands, 01 Apr. 2018, [Peer-reviewed]
English, Scientific journal, Constructions of numerical schemes for solving the radiative transfer equation (RTE) are crucial to evaluate light propagation inside photocatalytic systems. We develop accurate and efficient schemes of the three-dimensional and time-dependent RTE for numerical phantoms modeling aqueous titanium dioxide suspensions, in which the anisotropy of the forward-directed scattering varies and the strength of absorption is comparable to that of scattering. To improve the accuracy and efficiency of the numerical solutions, the forward-directed phase function is renormalized in the zeroth or first order with a small number of discrete angular directions. Then, we investigate the influences of the forward-directed scattering on the numerical solutions by comparing with the analytical solutions. The investigation shows that with the anisotropy factor less than approximately 0.7 corresponding to the moderate forward-directed scattering, the numerical solutions of the RTE using the both of the zeroth and first order renormalization approaches are accurate due to the reductions of the numerical errors of the phase function. With the anisotropy factor more than approximately 0.7 corresponding to the highly forward-directed scattering, the first order renormalization approach still provides the accurate results, while the zeroth order approach does not due to the large errors of the phase function. These results suggest that the developed scheme using the first order renormalization can provide accurate and efficient calculations of light propagation in photocatalytic systems. - Fine droplets generation induced by interactions between focused ultrasound and a liquid surface
Kazuya Seko, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe
Japanese Journal of Multiphase Flow, 32, 1, 59, 64, Mar. 2018, [Peer-reviewed]
Japanese, Scientific journal - Influence of surface roughness of high temperature wall on levitation of impacting droplet based on molecular dynamics simulation
Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
Surface Wettability Effects on Phase Change Phenomena (SWEP) workshop, 2018, [Peer-reviewed]
English, International conference proceedings - Numerical investigation of light and pressure propagation in biological tissue for model-based photoacoustic tomography
Kosuke Tabayashi, Hiroyuki Fujii, Kazumichi Kobayashi, Masao Watanabe
Extended Abstracts of The 9th JSME-KSME Thermal and Fluids Engineering Conference, TFEC9-1526, 1, 4, Oct. 2017, [Peer-reviewed]
English, International conference proceedings - Kinetic boundary condition in vapor-liquid two-phase system during unsteady net evaporation/condensation
Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
EUROPEAN JOURNAL OF MECHANICS B-FLUIDS, 64, 81, 92, ELSEVIER SCIENCE BV, Jul. 2017, [Peer-reviewed]
English, Scientific journal, Heat and mass transfer caused by nonequilibrium phase change (net evaporation/condensation) play a major role in a vapor-liquid two-phase flow. In general, liquid temperature changes with time because of the heat and mass transfer between the vapor and liquid phases; however, a precise investigation of the transport phenomena related to this temporal evolution of liquid temperature is still lacking. The aim of this study is to examine a kinetic boundary condition, which depends on liquid temperature, for the Boltzmann equation in a vapor-liquid two-phase system with unsteady net evaporation/condensation. In this study, we confirmed whether the kinetic boundary condition follows the temporal evolution of liquid temperature attributed to unsteady net evaporation/condensation by using the molecular simulation based on mean-field kinetic theory, and then we validated the accuracy of the kinetic boundary condition by solving the initial boundary value problem of the Boltzmann equation in unsteady net evaporation/condensation. These results showed that the kinetic boundary condition follows the temporal evolution of liquid temperature in the simulation setting of this study. Furthermore, we concluded that the kinetic boundary condition that depends on liquid temperature is guaranteed to be accurate even in unsteady net evaporation/condensation by considering the temporal evolution of liquid temperature. (C) 2016 Elsevier Masson SAS. All rights reserved. - Influence of condensation coefficient on spherical bubble collapse with evaporation and condensation
Shotaro Morikawa, Yuki Tatekura, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe, Koichi Sasaki
journal of Japan Society of Fluid Mechanics, 36, 2, 105, 108, 日本流体力学会, May 2017, [Peer-reviewed]
Japanese, Scientific journal - Modeling of light propagation in the human neck for diagnoses of thyroid cancers by diffuse optical tomography
H. Fujii, Y. Yamada, K. Kobayashi, M. Watanabe, Y. Hoshi
INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, 33, 5, e2826, WILEY, May 2017, [Peer-reviewed]
English, Scientific journal, Diffuse optical tomography using near-infrared light in a wavelength range from 700 to 1000nm has the potential to enable non-invasive diagnoses of thyroid cancers; some of which are difficult to detect by conventional methods such as ultrasound tomography. Diffuse optical tomography needs to be based on a physically accurate model of light propagation in the neck, because it reconstructs tomographic images of the optical properties in the human neck by inverse analysis. Our objective here was to investigate the effects of three factors on light propagation in the neck using the 2D time-dependent radiative transfer equation: (1) the presence of the trachea, (2) the refractive-index mismatch at the trachea-tissue interface, and (3) the effect of neck organs other than the trachea (spine, spinal cord, and blood vessels). There was a significant influence of reflection and refraction at the trachea-tissue interface on the light intensities in the region between the trachea and the front of the neck surface. Organs other than the trachea showed little effect on the light intensities measured at the front of the neck surface although these organs affected the light intensities locally. These results indicated the necessity of modeling the refractive-index mismatch at the trachea-tissue interface and the possibility of modeling other neck organs simply as a homogeneous medium when the source and detectors were far from large blood vessels. - Observation of the liquid film on a circular plate formed by a droplet train impingement
村木駿介, 山本翔也, 真田俊之, 渡部正夫
Transactions of the JSME, 848, 17, 00047, Apr. 2017, [Peer-reviewed] - Kinetic boundary conditions for vapor-gas binary mixture
Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe
MICROFLUIDICS AND NANOFLUIDICS, 21, 3, 1, 13, SPRINGER HEIDELBERG, Mar. 2017, [Peer-reviewed]
English, Scientific journal, Using molecular dynamics simulations, the present study investigated the precise characteristics of the binary mixture of condensable gas (vapor) and noncondensable gas (NC gas) molecules creating kinetic boundary conditions (KBCs) at a gas-liquid interface in equilibrium. We counted the molecules utilizing the improved two-boundary method proposed in previous studies by Kobayashi et al. (Heat Mass Trans 52: 1851-1859, 2016. doi: 10.1007/s00231-015-1700-6). In this study, we employed Ar for the vapor molecules, and Ne for the NC gas molecules. The present method allowed us to count easily the evaporating, condensing, degassing, dissolving, and reflecting molecules in order to investigate the detailed motion of the molecules, and also to evaluate the velocity distribution function of the KBCs at the interface. Our results showed that the evaporation and condensation coefficients for vapor and NC gas molecules decrease with the increase in the molar fraction of the NC gas molecules in the liquid. We also found that the KBCs can be specified as a function of the molar fraction and liquid temperature. Furthermore, we discussed the method to construct the KBCs of vapor and NC gas molecules. - Molecular Dynamics Study of Droplet Impact on High-Temperature Wall
Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
The 7th East Asia Mechanical and Aerospace Engineering Workshop, 2017, [Peer-reviewed]
English, International conference proceedings - Molecular Dynamics Simulation of the Role of the Wettability in the Droplet Impact on a High-temperature Wall
Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe
Extended Abstracts of the 9th JSME-KSME Thermal and Fluids Engineering Conference, TFEC9-1492, 2017, [Peer-reviewed]
English, International conference proceedings - Renormalization of the highly forward-peaked phase function using the double exponential formula for radiative transfer
Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi, Masao Watanabe
JOURNAL OF MATHEMATICAL CHEMISTRY, 54, 10, 2048, 2061, SPRINGER, Nov. 2016, [Peer-reviewed]
English, Scientific journal, Numerical calculation of photon migration in biological tissue using the radiative transfer equation (RTE) has attracted great interests in biomedical optics and imaging. Because biological tissue is a highly forward-peaked scattering medium, renormalization of the phase function in numerical calculation of the RTE is crucial. This paper proposes a simple approach of renormalizing the phase function by the double exponential formula, which was heuristically modified from the original one. Firstly, the validity of the proposed approach was tested by comparing numerical results for an average cosine of the polar scattering angle calculated by the proposed approach with those by the conventional approach in highly forward-peaked scattering. The results show that calculation of the average cosine converged faster using the proposed approach than using the conventional one as a total number of discrete angular directions increases. Next, the accuracy of the numerical solutions of the RTE using the proposed approach was examined by comparing the numerical solutions with the analytical solutions of the RTE in a homogeneous medium with highly forward-peaked scattering. It was found that the proposed approach reduced the errors of the numerical solutions from those using the conventional one especially at a small value of the total number of the directions. This result suggests that the proposed approach has a possibility to improve the accuracy for the numerical results of the RTE in the highly scattering medium. - Molecular dynamics study on evaporation and reflection of monatomic molecules to construct kinetic boundary condition in vapor-liquid equilibria
Kazumichi Kobayashi, Kazumasa Hori, Misaki Kon, Kiyofumi Sasaki, Masao Watanabe
HEAT AND MASS TRANSFER, 52, 9, 1851, 1859, SPRINGER, Sep. 2016, [Peer-reviewed]
English, Scientific journal, Using molecular dynamics simulations, the present study investigates the precise characteristics of evaporating and reflecting monatomic molecules (argon) composing a kinetic boundary condition (KBC) in a vapor-liquid equilibria. We counted the evaporating and reflecting molecules utilizing two boundaries (vapor and liquid boundaries) proposed by the previous studies (Meland et al. in Phys Fluids 16:223-243, 2004; Gu et al. in Fluid Phase Equilib 297:77-89, 2010). In the present study, we improved the method using the two boundaries incorporating the concept of the spontaneously evaporating molecular mass flux. The present method allows us to count the evaporating and reflecting molecules easily, to investigate the detail motion of the evaporating and reflecting molecules, and also to evaluate the velocity distribution function of the KBC at the vapor-liquid interface, appropriately. From the results, we confirm that the evaporating and reflecting molecules in the normal direction to the interface have slightly faster and significantly slower average velocities than that of the Maxwell distribution at the liquid temperature, respectively. Also, the stall time of the reflecting molecules at the interphase that is the region in the vicinity of the vapor-liquid interface is much shorter than those of the evaporating molecules. Furthermore, we discuss our method for constructing the KBC that incorporates condensation and evaporation coefficients. Based on these results, we suggest that the proposed method is appropriate for investigating KBC in various nonequilibrium states or multi-component systems. - Liquid temperature dependence of kinetic boundary condition at vapor-liquid interface
Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
INTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFER, 99, 317, 326, PERGAMON-ELSEVIER SCIENCE LTD, Aug. 2016, [Peer-reviewed]
English, Scientific journal, For the accurate description of heat and mass transfer through a vapor-liquid interface, the appropriate modeling of the interface during nonequilibrium phase change (net evaporation/condensation) is a crucial issue. The aim of this study is to propose a microscopic interfacial model which should be imposed at the interface as the kinetic boundary condition for the Boltzmann equation. In this study, we constructed the kinetic boundary condition for monoatomic molecules over a wide range of liquid temperature based on mean field kinetic theory, and we validated the accuracy of the constructed kinetic boundary condition by solving the boundary value problem of the Boltzmann equation. These results showed that we can impose the kinetic boundary condition at the interface by simply specifying liquid temperature and simulate the complex vapor-liquid two-phase flow induced by net evaporation/condensation. Furthermore, we applied the constructed kinetic boundary condition to the boundary condition for the fluid-dynamic type equations. This application enables us to deal with a large spatio-temporal scale of the interfacial dynamics in the vapor-liquid two-phase system with net evaporation/condensation. (C) 2016 Elsevier Ltd. All rights reserved. - Gas compression and dissolution in closed end tubes by applying pressure (Liquid infiltration characteristics into fine structure by pressure)
SANADA Toshiyuki, NOZAKI Hiroshi, WATANABE Masao
Transactions of the JSME, 82, 838, Jun. 2016, [Peer-reviewed]
Japanese, Scientific journal - Early stage of nanodroplet impact on solid wall
Kazumichi Kobayashi, Kazuki Konno, Hisao Yaguchi, Hiroyuki Fujii, Toshiyuki Sanada, Masao Watanabe
PHYSICS OF FLUIDS, 28, 3, AMER INST PHYSICS, Mar. 2016, [Peer-reviewed]
English, Scientific journal, In this study, we investigated nanodroplet spreading at the early stage after the impact using molecular dynamics simulations by changing the magnitude of the intermolecular force between the liquid and wall molecules. We showed that the droplet deformation after the impact greatly depends on the intermolecular force. The temporal evolution of the spreading diameters was measured by the cylindrical control volume for several molecular layers in the vicinity of the wall. At the early stage of the nanodroplet impact, the normalized spreading radius of the droplet is proportional to the square root of the normalized time, (t) over cap. This result is understood by the geometrical consideration presented by Rioboo et al. ["Time evolution of liquid drop impact onto solid, dry surfaces," Exp. Fluids 33, 112-124 (2002)]. In addition, we found that as the intermolecular force between the liquid and wall becomes stronger, the normalized spreading diameter of the first molecular layer on the wall remains less dependent on the impact velocity. Furthermore, the time evolution of the droplet spreading changes from root(t) over cap to log (t) over cap with time. (C) 2016 AIP Publishing LLC. - Near-infrared optical properties of white bread using the light propagation model
Hiroyuki Fujii, Goro Nishimura, Kiyohito Hattori, Kazumichi Kobayashi, Masao Watanabe
Proceeding of the fifth Asian NIR symposium (ANS2016), 2016, P-86, 288, 289, 2016, [Peer-reviewed]
English, International conference proceedings - Quantitative method to determine the optical properties of melons by the photon diffusion equation
Kiyohito Hattori, Goro Nishimura, Hiroyuki Fujii, Kazumichi Kobayashi, Masao Watanabe
Proceeding of the fifth Asian NIR symposium (ANS2016), 2016, O-6, 72, 73, 2016, [Peer-reviewed]
English, International conference proceedings - Normalisation Method of Highly Forward-peaked Scattering Phase Function using the Double Exponential Formula for Radiative Transfer
Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi, Masao Watanabe
Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016), 1790, 050002, 1, 4, AMER INST PHYSICS, 2016, [Peer-reviewed]
English, International conference proceedings, Numerical calculation of photon migration in biological tissue using the radiative transfer equation (RTE) has attracted great interests in biomedical optics and imaging. Because biological tissue is a highly forward-peaked scattering medium, a normalization of scattering phase function in the RTE is crucial. This paper proposes a simple way of normalizing the phase function by the double exponential formula, which is heuristically modified from the original one. The proposed method is validated by the agreement between the numerical solution of the RTE with the proposed method and analytical solution of the RTE for the case of a highly forward-peaked scattering medium, while the numerical solutions with conventional normalization methods disagree with the analytical solution. This result suggests the proposed method is accurate in numerical calculation of the RTE. - Numerical Study of Photon Migration in the Presence of a Void Region using the radiative Transfer and Diffusion Equations
Erina Miyakawa, Hiroyuki Fujii, Kiyohito Hattori, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
Proceedings of the International Conference of Computational Methods in Sciences and Engineering 2016 (ICCMSE-2016), 1790, 050003, AMER INST PHYSICS, 2016, [Peer-reviewed]
English, International conference proceedings, Diffuse optical tomography (DOT), which is still under development, has a potential to enable non-invasive diagnoses of thyroid cancers in the human neck using the near-infrared light. This modality needs a photon migration model because scattered light is used. There are two types of photon migration models: the radiative transport equation (RTE) and diffusion equation (DE). The RTE can describe photon migration in the human neck with accuracy, while the DE enables an efficient calculation. For developing the accurate and efficient model of photon migration, it is crucial to investigate a condition where the DE holds in a scattering medium including a void region under the refractive-index mismatch at the void boundary because the human neck has a trachea (void region) and the refractive indices are different between the human neck and trachea. Hence, in this paper, we compare photon migration using the RTE with that using the DE in the medium. The numerical results show that the DE is valid under the refractive-index match at the void boundary even though the void region is near the source and detector positions. Under the refractive-index mismatch at the boundary, the numerical results using the DE disagree with those using the RTE when the void region is near the source and detector positions. This is probably because the anisotropy of the light scattering remains around the void boundary. - Molecular Dynamics Simulation on Kinetic Boundary Conditions of Gas-Vapor Binary Mixture
Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe
30TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS (RGD 30), 1786, 110002, AMER INST PHYSICS, 2016, [Peer-reviewed]
English, International conference proceedings, The aim of this study is to construct the kinetic boundary condition for Ar-Ne binary mixture in equilibrium using molecular dynamics (MD) simulations. The temperature of the MD simulation system is 85 K; Ar molecules behave as condensable gas (vapor), and Ne molecules behave as non-condensable gas (gas). In this simulation, we utilize the two-boundary method improved by our previous study to investigate behaviors of Ar and Ne molecules at the interface. From the results, we can obtain the molecular mass fluxes at the interface, and evaluate the values of evaporation and condensation coefficients of Ar (vapor) and Ne (gas) molecules. - Molecular Simulation of Evaporation Mass Flux during Net Evaporation/Condensation
Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
30TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS (RGD 30), 1786, 110001, AMER INST PHYSICS, 2016, [Peer-reviewed]
English, International conference proceedings, To examine the transport phenomena in a vaporliquid two-phase system attributed to the phase change, a proper specification of the mass flux at a vaporliquid interface is crucial. Since the mass flux induced by the phase change originates from the motion of molecules in the vicinity of the vaporliquid interface, a continuum description such as the fluid dynamic based approach is inappropriate. An essential way to obtain this mass flux is the analysis of the Boltzmann equation with a certain boundary condition, that is, the kinetic boundary condition. In this study, we examined the definition and the estimation procedure of the evaporation coefficient, which is included in the kinetic boundary condition, at the vaporliquid interface with phase change, especially at higher temperature for hard-sphere molecules. As the result, we confirmed that a conventional definition of the evaporation coefficient is accurate even if liquid temperature is higher. Moreover, we also confirmed that the evaporation coefficient is only the function of liquid temperature by counting the number of molecules passing through the two boundaries which are placed near the vaporliquid interface. - Numerical modeling of photon migration in human neck based on the radiative transport equation
Hiroyuki Fujii, Shinpei Okawa, Ken Nadamoto, Eiji Okada, Yukio Yamada, Yoko Hoshi, Masao Watanabe
Journal of Applied Nonlinear Dynamics, 5, 1, 117, 125, L and H Scientific Publishing, LLC, 2016, [Peer-reviewed]
English, Scientific journal, Biomedical optical imaging has a possibility of a comprehensive di- agnosis of thyroid cancer in conjunction with ultrasound imaging. For improvement of the optical imaging, this study develops a higher order scheme for solving the time-dependent radiative transport equa- tion (RTE) by use of the finite-difference and discrete-ordinate meth- ods. The accuracy and efficiency of the developed scheme are ex- amined by comparison with the analytical solutions of the RTE in homogeneous media. Then, the developed scheme is applied to de- scribing photon migration in the human neck model. The numerical simulations show complex behaviors of photon migration in the hu- man neck model due to multiple diffusive reflection near the trachea. - Estimation of Evaporation Mass Flux at Vapor-Liquid Interface during Nonequilibrium Evaporation/condensation
Kazumichi Kobayashi, Kazumasa Hori, Misaki Kon, Kiyofumi Sasaki, Masao Watanabe
JAPANESE JOURNAL OF MULTIPHASE FLOW, 29, 5, 493, 500, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, Nov. 2015, [Peer-reviewed]
Japanese, Scientific journal, The aim of this study is to confirm the existence of a spontaneous evaporation molecular mass flux which takes a constant value independent of the degree of net evaporation/condensation. We carried out the numerical simulation based on the mean field kinetic theory during net evaporation/condensation and estimated the evaporation and reflection molecular mass fluxes by using a pair of boundaries. The simulation results showed that the reflection molecular mass flux varies with the increase of the degree of nonequilibrium, and the evaporation molecular mass flux takes a constant value during net evaporation and condensation. - How do bubbles reduce the speed of sound in a bubbly liquid in a duct?
Junya Kawahara, Masao Watanabe, Kazumichi Kobayashi
Mechanical Engineering Letters, 1, 115-00464-15-00464, Oct. 2015, [Peer-reviewed]
English, Scientific journal - 低圧力環境下での高速液滴衝突により発生する液膜流れ
KATO MASAYA, WATANABE MASAO, KOBAYASHI KAZUMICHI, SANADA TOSHIYUKI
混相流, 28/29, 5/1, 531, 537, 15 Mar. 2015
Japanese - 22aAK-12 Effect of nonequilibrium velocity distribution function to vapor flows
Kon M., Kobayashi K., Watanabe M.
Meeting Abstracts of the Physical Society of Japan, 70, 2975, 2975, The Physical Society of Japan (JPS), 2015
Japanese - A coupling model of the radiative transport equation for calculating photon migration in biological tissue
Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi, Masao Watanabe
Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 9792, SPIE, 2015, [Peer-reviewed]
English, International conference proceedings, Development of a physically accurate and computationally efficient photon migration model for turbid media is crucial for optical computed tomography such as diffuse optical tomography. For the development, this paper constructs a space-time coupling model of the radiative transport equation with the photon diffusion equation. In the coupling model, a space-time regime of the photon migration is divided into the ballistic and diffusive regimes with the interaction between the both regimes to improve the accuracy of the results and the efficiency of computation. The coupling model provides an accurate description of the photon migration in various turbid media in a wide range of the optical properties, and reduces computational loads when compared with those of full calculation of the RTE. - Numerical study of light propagation in agricultural products for non-destructive assessment of food quality
Kiyohito Hattori, Hiroyuki Fujii, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 9792, SPIE, 2015, [Peer-reviewed]
English, International conference proceedings, An accurate determination of optical properties of agricultural products is crucial for non-destructive assessment of food quality. For the determination, light intensity is measured at the surface of the product
then, inverse analysis is employed based on a light propagation model such as the radiative transfer equation (RTE). The inverse analysis requires high computational loads because the light intensity is numerically calculated using the model every time the optical properties are changed. For the calculation, we propose an efficient technique by combining a numerical solution with an analytical solution of the RTE, and investigate the validity of the technique in a two-dimensional homogeneous circular medium which is regarded as a light propagation model with optical properties of kiwifruit. The proposed technique can provide accurate results of the light intensity in change of the optical properties, and the accuracy is less dependent on the boundary conditions and source-detector angles. In addition, the technique can reduce computation time compared with that for numerical calculation of the RTE. These results indicate usefulness of the proposed technique for the inverse analysis. - Numerical modeling of photon migration in the cerebral cortex of the living rat using the radiative transport equation
Hiroyuki Fujii, Shinpei Okawa, Ken Nadamoto, Eiji Okada, Yukio Yamada, Yoko Hoshi, Masao Watanabe
Progress in Biomedical Optics and Imaging - Proceedings of SPIE, 9333, SPIE, 2015, [Peer-reviewed]
English, International conference proceedings, Accurate modeling and efficient calculation of photon migration in biological tissues is requested for determination of the optical properties of living tissues by in vivo experiments. This study develops a calculation scheme of photon migration for determination of the optical properties of the rat cerebral cortex (ca 0.2 cm thick) based on the three-dimensional time-dependent radiative transport equation assuming a homogeneous object. It is shown that the time-resolved profiles calculated by the developed scheme agree with the profiles measured by in vivo experiments using near infrared light. Also, an efficient calculation method is tested using the delta-Eddington approximation of the scattering phase function. - Numerical modeling of photon migration in the cerebral cortex of the living rat using the radiative transport equation
Hiroyuki Fujii, Shinpei Okawa, Ken Nadamoto, Eiji Okada, Yukio Yamada, Yoko Hoshi, Masao Watanabe
BIOMEDICAL APPLICATIONS OF LIGHT SCATTERING IX, 9333, 933313, 1, 6, SPIE-INT SOC OPTICAL ENGINEERING, 2015, [Peer-reviewed]
English, International conference proceedings, Accurate modeling and efficient calculation of photon migration in biological tissues is requested for determination of the optical properties of living tissues by in vivo experiments. This study develops a calculation scheme of photon migration for determination of the optical properties of the rat cerebral cortex (ca 0.2 cm thick) based on the three-dimensional time-dependent radiative transport equation assuming a homogeneous object. It is shown that the time-resolved profiles calculated by the developed scheme agree with the profiles measured by in vivo experiments using near infrared light. Also, an efficient calculation method is tested using the delta-Eddington approximation of the scattering phase function. - A coupling model of the radiative transport equation for calculating photon migration in biological tissue
Hiroyuki Fujii, Shinpei Okawa, Yukio Yamada, Yoko Hoshi, Masao Watanabe
BIOPHOTONICS JAPAN 2015, 9792, 979214, 1, 5, SPIE-INT SOC OPTICAL ENGINEERING, 2015, [Peer-reviewed]
English, International conference proceedings, Development of a physically accurate and computationally efficient photon migration model for turbid media is crucial for optical computed tomography such as diffuse optical tomography. For the development, this paper constructs a space-time coupling model of the radiative transport equation with the photon diffusion equation. In the coupling model, a space-time regime of the photon migration is divided into the ballistic and diffusive regimes with the interaction between the both regimes to improve the accuracy of the results and the efficiency of computation. The coupling model provides an accurate description of the photon migration in various turbid media in a wide range of the optical properties, and reduces computational loads when compared with those of full calculation of the RTE. - Numerical study of light propagation in agricultural products for non-destructive assessment of food quality
Kiyohito Hattori, Hiroyuki Fujii, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe
BIOPHOTONICS JAPAN 2015, 9792, 97921A, SPIE-INT SOC OPTICAL ENGINEERING, 2015, [Peer-reviewed]
English, International conference proceedings, An accurate determination of optical properties of agricultural products is crucial for non-destructive assessment of food quality. For the determination, light intensity is measured at the surface of the product; then, inverse analysis is employed based on a light propagation model such as the radiative transfer equation (RTE). The inverse analysis requires high computational loads because the light intensity is numerically calculated using the model every time the optical properties are changed. For the calculation, we propose an efficient technique by combining a numerical solution with an analytical solution of the RTE, and investigate the validity of the technique in a two-dimensional homogeneous circular medium which is regarded as a light propagation model with optical properties of kiwifruit. The proposed technique can provide accurate results of the light intensity in change of the optical properties, and the accuracy is less dependent on the boundary conditions and source-detector angles. In addition, the technique can reduce computation time compared with that for numerical calculation of the RTE. These results indicate usefulness of the proposed technique for the inverse analysis. - Numerical simulation of bubble collapse and the transfer of vapor and noncondensable gas through the bubble interface using the ghost fluid method
Y. Jinbo, K. Kobayashi, M. Watanabe, H. Takahira
9TH INTERNATIONAL SYMPOSIUM ON CAVITATION (CAV2015), 656, 1, 5, IOP PUBLISHING LTD, 2015, [Peer-reviewed]
English, International conference proceedings, The ghost fluid method is improved to include heat and mass transfer across the gas-liquid interface during the bubble collapse in a compressible liquid. This transfer is due to both nonequilibrium phase transition at the interface and diffusion of the noncondensable gas across the interface. In the present method, the ghost fluids are defined with the intention of conserving the total mass, momentum, and energy, as well as the mass of each component while considering the heat and mass fluxes across the interface. The gas phase inside the bubble is a mixture of vapor and noncondensable gas, where binary diffusion between the mixture components is taken into account. The gas diffusion in the surrounding liquid is also considered. This method is applied to a simulation of a single spherical bubble collapse with heat and mass transfer across the interface in a compressible liquid. When noncondensable gas is present, it accumulates near the interface due to vapor condensation, thereby preventing further condensation. This results in a weaker bubble collapse than the case without noncondensable gas. - Photoresist and Thin Metal Film Removal by Steam and Water Mixed Spray
Toshiyuki Sanada, Masao Watanabe
JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY, 28, 2, 289, 292, TECHNICAL ASSOC PHOTOPOLYMERS,JAPAN, 2015, [Peer-reviewed]
English, Scientific journal - Observation of Water-Droplet Impacts with Velocities of O(10 m/s) and Subsequent Flow Field
Y. Tatekura, T. Fujikawa, Y. Jinbo, T. Sanada, K. Kobayashi, M. Watanabe
ECS JOURNAL OF SOLID STATE SCIENCE AND TECHNOLOGY, 4, 9, N117, N123, ELECTROCHEMICAL SOC INC, 2015, [Peer-reviewed]
English, Scientific journal, A two-fluid spray cleaning technique has been gaining popularity as a cleaning process in the semiconductor industry. The most essential physical process in this technique is the impact of droplets with a velocity of O(10 m/s) on a solid surface. This study aims to experimentally and numerically investigate water-droplet impacts with velocities of up to 50 m/s and their subsequent flow fields, especially the gas flow field in the strictly limited area in the vicinity of the contact line. First, we experimentally evaluated the velocity of the splash and numerically calculated the gas velocities. Comparison of these velocities supported our assumption that the maximum gas velocity may be on approximately the same order as the velocity of the splash. Therefore, we concluded that the gas velocity field of the order of 500 m/s indeed develops at the impact of droplet with a velocity of the order of 50 m/s. Moreover, we determined that the gas pressure was of the order of 1.0 MPa by numerical analysis. Such a high pressure leads to shock wave propagation, which can contribute to the cleaning process in semiconductor production. (C) 2015 The Electrochemical Society. All rights reserved. - Study on Pressure Wave Propagation in a Liquid Containing Spherical Bubbles in a Rectangular Duct
Junya Kawahara, Masao Watanabe, Kazumichi Kobayashi
9TH INTERNATIONAL SYMPOSIUM ON CAVITATION (CAV2015), 656, 1, 5, IOP PUBLISHING LTD, 2015, [Peer-reviewed]
English, International conference proceedings, Pressure wave propagation in a liquid containing several bubbles is numerically investigated. We simulate liner plane wave propagation in a liquid containing 10 spherical bubbles in a rectangular duct with the equation of motion for N spherical bubbles. The sound pressures of the reflected waves from the rigid walls are calculated by using the method of images. The result shows that the phase velocity of the pressure wave propagating in the liquid containing 10 spherical bubbles in the duct agrees well with the low-frequency speed of sound in a homogeneous bubbly liquid. - Method of determining kinetic boundary conditions in net evaporation/condensation
Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
PHYSICS OF FLUIDS, 26, 7, 072003, AMER INST PHYSICS, Jul. 2014, [Peer-reviewed]
English, Scientific journal, The aim of the present study is to develop the method of determining the kinetic boundary condition (KBC) at a vapor-liquid interface in net evaporation/condensation. We proposed a novel method for determining the KBC by combining the numerical simulations of the mean field kinetic theory and the molecular gas dynamics. The method was evaluated on steady vapor flow between two liquid slabs at different temperatures. A uniform net mass flux in the vapor phase induced by net evaporation and condensation is obtained from the numerical simulation of the mean field kinetic theory for both vapor and liquid phases. The KBC was specified by using the uniform net mass flux, and the numerical simulation of the molecular gas dynamics was conducted for the vapor phase. Comparing the macroscopic variables in the vapor phase obtained from both numerical simulations, we can validate the KBC whether the appropriate solutions are obtained. Moreover, the evaporation and condensation coefficients were estimated uniquely. The results showed that the condensation and evaporation coefficients were identical and constant in net evaporation. On the other hand, in net condensation, the condensation coefficient increased with the collision molecular mass flux. We also presented the applicable limit of the KBC which is assumed to be the isotropic Gaussian distribution at the liquid temperature. From these results, the KBCs in net evaporation and condensation, which enable the exact macroscopic variables to be determined, were proposed. (C) 2014 AIP Publishing LLC. - Molecular Dynamics Simulation on Evaporation Molecules in a Vapor-Liquid Equilibrium State
Kazumichi Kobayashi, Kazumasa Hori, Hisao Yaguchi, Masao Watanabe
PROCEEDINGS OF THE 29TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS, 1628, 404, 410, AMER INST PHYSICS, 2014, [Peer-reviewed]
English, International conference proceedings, By using molecular dynamics simulations of argon molecules, the present study investigates molecular evaporation and reflection in equilibrium at a vapor liquid interface, which involves the kinetic boundary condition (KBC) of the Boltzmann equation. The present method allows evaporation and reflection molecules to be selected naturally at the vapor-liquid interphase. Based on the results, we confirm that the evaporation molecules in the equilibrium state behave almost similar to spontaneous evaporation molecules (as determined by virtual vacuum evaporation simulations). Furthermore, we find that the velocity distribution of reflection molecules in the normal direction to the boundary is lower than the Maxwell distribution at the liquid temperature. - Numerical Analysis of Kinetic Boundary Conditions at Net Evaporation/condensation Interfaces in Various Liquid Temperatures Based on Mean-field Kinetic Theory
Misaki Kon, Kazumichi Kobayashi, Masao Watanabe
PROCEEDINGS OF THE 29TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS, 1628, 398, 403, AMER INST PHYSICS, 2014, [Peer-reviewed]
English, International conference proceedings, This study aims to investigate the liquid temperature dependency of the kinetic boundary condition at a vapor-liquid interface in net evaporation/condensation. The numerical simulations based on the mean-field kinetic theory and the molecular gas dynamics in the cases of various liquid temperatures were carried out. We focused on two important issues for the kinetic boundary condition; one is to investigate the applicable limit of the kinetic boundary condition which is assumed to be the isotropic velocity distribution at the liquid temperature and the other is to estimate the value of the condensation coefficient included in the kinetic boundary condition. The simulation results showed that the applicable limit of the isotropic velocity distribution in net evaporation/condensation practically independent from the liquid temperature. Furthermore, the condensation coefficients in net evaporation/condensation depend significantly on the liquid temperature; the condensation coefficient is constant and equal to the evaporation coefficient in net evaporation, while, in net condensation, the condensation coefficient increases with the increase of the degree of nonequilibrium. - Effect of Surrounding Gas Species of Two Fluid Jet Method for Surface Cleaning
SANADA TOSHIYUKI, WATANABE MASAO
エアロゾル研究, 29, 4, 236-240 (J-STAGE), 2014
Japanese - Analysis of Discrete Model of Spherical Bubbles with Interaction : Acoustic Characteristics of Bubbly Liquids (Mathematical theory, modeling, and applications of nonlinear wave research)
KAWAHARA Junya, KOBAYASHI Kazumichi, WATANABE Masao
RIMS Kokyuroku, 1847, 10, 15, 京都大学, Aug. 2013
Japanese - Evaporation and Condensation Coefficients of Methanol at Room Temperature, and Consideration of Kinetic Boundary Condition
KOBAYASHI KAZUMICHI, MORI SHINGO, WATANABE YUSUKE, WATANABE MASAO, FUJIKAWA SHIGEO
熱物性, 27, 1, 9, 14, JAPAN SOCIETY OF THERMOPHYSICAL PROPERTIES, 28 Feb. 2013
Japanese, The growth rate of a liquid film formed on a shock-tube endwall due to condensation of methanol vapor behind a shock wave reflected at the endwall is measured by an optical interferometer at room temperature, and it is analyzed with the aid of molecular gas dynamics in order to deduce evaporation and condensation coefficients. The measurements are done in the region of 1 ≤σ / ρ*<1.3, where σ / ρ* is nonequilibrium degree. The condensation coefficient is almost the same value as the evaporation coefficient (=0.86) in 1 ≤σ / ρ* <1.05 and decreases to the smaller values than the evaporation coefficient in σ / ρ*>1.05, and the kinetic boundary condition is valid in 1 ≤σ / ρ*<1.05. - Nonlinear Wave Propagation in Bubbly Liquids
T. Yano, T. Kanagawa, M. Watanabe, S. Fujikawa
Bubble Dynamics and Shock Waves, 107, 140, Springer Berlin Heidelberg, 2013
In book - Molecular Dynamics Study of Nano-scale Liquid-gas Interface Inspired by Fuel Cell Catalyst Layer
Youngmin Kim, Hisao Yaguchi, Nobuyuki Oshima, Masao Watanabe, Kazumichi Kobayashi
ASME 2013 11th International Conference on Nanochannels, 2013, [Peer-reviewed] - 蒸発・凝縮をともなう非線形共鳴音波
INABA MASASHI, YANO TAKERU, KOBAYASHI KAZUMICHI, WATANABE MASAO
ながれ, 31, 6, 487, 490, 日本流体力学会, 25 Dec. 2012
Japanese - 水蒸気と水の混合噴流による表面薄膜はく離(アルミニウム蒸着膜のはく離特性と表面温度変化の影響)
真田俊之, 橋本健太郎, 林田充司, 小林一道, 渡部正夫
混相流, 26, 2, 172, 177, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, 15 Jun. 2012
Japanese, We have been developing a novel surface cleaning technique using steam and water mixed spray. Our technique shows great efficiency in removing thin surface film such as photo-resist film. However, the film-removal mechanism has not been clarified yet. One possible film-removal mechanism is the local heat expansion due to the difference of coefficients of linear expansion between film and substrate. In this study, we studied the removal characteristics of deposited aluminum film on a glass surface by spraying steam-water or air-water mixed spray. The surface temperature changes caused by the spray were carefully measured. We found that the steam and water mixed spray that increases the surface temperature can remove the film while the air and water mixed spray cannot. These results indicate that the difference of coefficients of linear expansion between film and substrate may not be the dominant factor in the film removal by the steam and water mixed spray. - 固体表面に衝突する単一液滴変形過程の観察(液滴物性,対象物表面粗さ及び周囲気体圧力の影響)
櫻井泰貴, 小林一道, 藤川俊秀, 真田俊之, 渡部正夫
混相流, 26, 2, 164, 171, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, 15 Jun. 2012
Japanese, In the cleaning processes of manufacturing semiconductor devices, two-fluid spray cleaning technique is widely used: however, the detailed cleaning mechanism has not been clarified yet. In this study, we focus our attention to the elementary process of this cleaning technique, i.e. a single droplet impact on a solid surface. We experimentally observe impact of single droplet on a rigid solid surface with the use of high-speed photography, and we discuss the deformation of the droplet. Especially we focus on the effects of surfaces tension, surface roughness and surrounding pressure. Water droplets always create lamella during spreading after the impact on a smooth surface in the atmospheric pressure condition. Either decrease of the surface tension or increase of the surface roughness causes droplet splash. However, decrease of the surrounding gas pressure makes droplets always create lamella even in the cases with low surface tension and rough surfaces. - Thin Film Removal by Steam and Water Mixed Spray : Removal Characteristic of Deposited Aluminum Film and Effects of Surface Temperature Change
SANADA Toshiyuki, HASHIMOTO Kentaro, HAYASHIDA Atsushi, KOBAYASHI Kazumichi, WATANABE Masao
JAPANESE JOURNAL OF MULTIPHASE FLOW, 26, 2, 172, 177, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, 15 Jun. 2012
Japanese, We have been developing a novel surface cleaning technique using steam and water mixed spray. Our technique shows great efficiency in removing thin surface film such as photo-resist film. However, the film-removal mechanism has not been clarified yet. One possible film-removal mechanism is the local heat expansion due to the difference of coefficients of linear expansion between film and substrate. In this study, we studied the removal characteristics of deposited aluminum film on a glass surface by spraying steam-water or air-water mixed spray. The surface temperature changes caused by the spray were carefully measured. We found that the steam and water mixed spray that increases the surface temperature can remove the film while the air and water mixed spray cannot. These results indicate that the difference of coefficients of linear expansion between film and substrate may not be the dominant factor in the film removal by the steam and water mixed spray. - Observation of Deformation of Single Droplet Impact on Solid Surface : Effects of Liquid Properties, Surface Roughness and Surrounding Gas Pressure
SAKURAI Yasuki, KOBAYASHI Kazumichi, FUJIKAWA Toshihide, SANADA Toshiyuki, WATANABE Masao
JAPANESE JOURNAL OF MULTIPHASE FLOW, 26, 2, 164, 171, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, Jun. 2012, [Peer-reviewed]
Japanese, Scientific journal, In the cleaning processes of manufacturing semiconductor devices, two-fluid spray cleaning technique is widely used: however, the detailed cleaning mechanism has not been clarified yet. In this study, we focus our attention to the elementary process of this cleaning technique, i.e. a single droplet impact on a solid surface. We experimentally observe impact of single droplet on a rigid solid surface with the use of high-speed photography, and we discuss the deformation of the droplet. Especially we focus on the effects of surfaces tension, surface roughness and surrounding pressure. Water droplets always create lamella during spreading after the impact on a smooth surface in the atmospheric pressure condition. Either decrease of the surface tension or increase of the surface roughness causes droplet splash. However, decrease of the surrounding gas pressure makes droplets always create lamella even in the cases with low surface tension and rough surfaces. - Linear theory of sound waves with evaporation and condensation
Masashi Inaba, Takeru Yano, Masao Watanabe
FLUID DYNAMICS RESEARCH, 44, 2, IOP PUBLISHING LTD, Apr. 2012, [Peer-reviewed]
English, Scientific journal, An asymptotic analysis of a boundary-value problem of the Boltzmann equation for small Knudsen number is carried out for the case when an unsteady flow of polyatomic vapour induces reciprocal evaporation and condensation at the interface between the vapour and its liquid phase. The polyatomic version of the Boltzmann equation of the ellipsoidal statistical Bhatnagar-Gross-Krook (ES-BGK) model is used and the asymptotic expansions for small Knudsen numbers are applied on the assumptions that the Mach number is sufficiently small compared with the Knudsen number and the characteristic length scale divided by the characteristic time scale is comparable with the speed of sound in a reference state, as in the case of sound waves. In the leading order of approximation, we derive a set of the linearized Euler equations for the entire flow field and a set of the boundary-layer equations near the boundaries (the vapour-liquid interface and simple solid boundary). The boundary conditions for the Euler and boundary-layer equations are obtained at the same time when the solutions of the Knudsen layers on the boundaries are determined. The slip coefficients in the boundary conditions are evaluated for water vapour. A simple example of the standing sound wave in water vapour bounded by a liquid water film and an oscillating piston is demonstrated and the effect of evaporation and condensation on the sound wave is discussed. - NONLINEAR PROPAGATION OF SOUND BEAM IN NONUNIFORM BUBBLY LIQUIDS
Tetsuya Kanagawa, Takeru Yano, Junya Kawahara, Kazumichi Kobayashi, Masao Watanabe, Shigeo Fujikawa
FLUID MEASUREMENTS AND INSTRUMENTATION CAVITATION AND MULTIPHASE FLOW ADVANCES IN FLUIDS ENGINEERING EDUCATION MICROFLUIDICS, VOL 2, 237, 241, AMER SOC MECHANICAL ENGINEERS, 2012, [Peer-reviewed]
English, International conference proceedings, Nonlinear propagation of weakly diffracted sound beams in a weakly nonuniform bubbly liquid is analytically studied based on the method of multiple scales and scaling relations of some physical parameters. The system of basic equations consists of the conservation equations of mass and momentum for gas and liquid in a two-flui model, the Keller equation for bubble wall, the state equations for gas and liquid, and so on. The compressibility of liquid is taken into account and this leads to the wave attenuation due to bubble oscillations. It is assumed that the spatial distribution of the number density of bubbles in an initial state at rest is a slowly varying function of space coordinates and the amplitude of its variation is small compared with a mean number density. As a result, a Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation with dispersion and nonuniform effects for a low frequency and long wavelength case and a nonlinear Schrodinger (NLS) equation with dissipation, diffraction, and nonuniform effects are derived from the basic equations. - ULTRASOUND BEAM RADIATED FROM CIRCULAR PISTON IN BUBBLY LIQUIDS: NONLINEAR ANALYSIS FOR ENVELOPE OF SHORT WAVES WITH DIFFRACTION EFFECT
Junya Kawahara, Tetsuya Kanagawa, Takeru Yano, Kazumichi Kobayashi, Masao Watanabe, Shigeo Fujikawa
FLUID MEASUREMENTS AND INSTRUMENTATION CAVITATION AND MULTIPHASE FLOW ADVANCES IN FLUIDS ENGINEERING EDUCATION MICROFLUIDICS, VOL 2, 251, 256, AMER SOC MECHANICAL ENGINEERS, 2012, [Peer-reviewed]
English, International conference proceedings, A weakly diffracted ultrasound beam radiated from a circular piston placed in a bubbly liquid is formulated in terms of a wave equation based on scaling relations of physical parameters [1]: typical propagation speed, period, wavelength, and diameter of beam. We derive a nonlinear evolution equation for the modulation of quasi-monochromatic waves for the case of a short wavelength with a moderately high frequency from a set of basic equations for bubbly flows: conservation equations of mass and momentum for gas and liquid in a two-fluid model, Keller's equation for bubble wall motion, state equations for gas and liquid, and so on. The compressibility of liquid is taken into account, and thus the waves are attenuated due to bubble oscillations. The viscosity of gas, heat conduction in gas and liquid, and phase change across bubble wall are ignored. As a result, the nonlinear Schrodinger equation for the envelope of the beam with diffraction effect is derived from the basic equations. For plane waves the diffraction term does not appear, and hence our equation is reduced to the original nonlinear Schrodinger equation [1]. - Observation of Deformation of Single Droplet Impact on Solid Surface (Effects of Liquid Properties, Surface Roughness and Surrounding Gas Pressure)
Sakurai, Y, Kobayashi, K, Fujikawa, T, Sanada, T, Watanabe,M
Japanese J. Multiphase Flow, 98, 6, 515, 521, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, 2012, [Peer-reviewed]
Japanese, In the cleaning processes of manufacturing semiconductor devices, two-fluid spray cleaning technique is widely used: however, the detailed cleaning mechanism has not been clarified yet. In this study, we focus our attention to the elementary process of this cleaning technique, i.e. a single droplet impact on a solid surface. We experimentally observe impact of single droplet on a rigid solid surface with the use of high-speed photography, and we discuss the deformation of the droplet. Especially we focus on the effects of surfaces tension, surface roughness and surrounding pressure. Water droplets always create lamella during spreading after the impact on a smooth surface in the atmospheric pressure condition. Either decrease of the surface tension or increase of the surface roughness causes droplet splash. However, decrease of the surrounding gas pressure makes droplets always create lamella even in the cases with low surface tension and rough surfaces. - Order Estimation of Physical Processes in Dynamics of Steam-Water Mixed Spray Cleaning Technique
Masao Watanabe, Toshiyuki Sanada, Takashi Mashiko, Atsushi Hayashida
ULTRA CLEAN PROCESSING OF SEMICONDUCTOR SURFACES X, 187, 141, +, TRANS TECH PUBLICATIONS LTD, 2012, [Peer-reviewed]
English, International conference proceedings, We have been developing an innovative ultra-low environmental load cleaning technique by the use of steam-water mixed spray. We showed that this technique is quite effective in both cleaning and photo-resist stripping. We also found that the physical force associated with steam-water mixed spray is greater than that with air-water mixed spray; hence we proposed that the condensation plays an important role in this cleaning technique. In order to discuss further this mechanism, we perform the order estimation of physical processes in dynamics of liquid droplet moving in vapor flow impacting on a solid interface in this study. Results show that droplet impact velocity can be reduced while the droplet approaches to the solid surface. However, the vapor in the gap can condensate to either the liquid droplet or the solid surface with the velocity whose order of magnitude cannot be negligible compared to the impact velocity; hence the amount of vapor that should be pushed out from gap can be drastically reduced, This condensation results in the significant reduction of viscous force. This reduction of force with the existence of condensation reduces the impact velocity deceleration. Consequently significantly large impact pressure is generated. - Measurement of adhesion force of resist to wafer by using SAICAS: Characteristics of lift-off of resist by steam-water mixed spray
Takashi Mashiko, Toshiyuki Sanada, Hideo Horibe, Itsuo Nishiyama, Masao Watanabe, Atsushi Hayashida
ULTRA CLEAN PROCESSING OF SEMICONDUCTOR SURFACES X, 187, 85, +, TRANS TECH PUBLICATIONS LTD, 2012, [Peer-reviewed]
English, International conference proceedings, We performed two experiments on resist-coated wafers. In the measurement of the resist-wafer adhesivity, we confirmed that it is significantly increased by an HMDS layer in between. In the resist-removal experiment using steam-water mixed spray, we found that the area of resist removal is limited within the area of spray application if HMDS is used, otherwise the former can be larger than the latter. These results suggest that the resist removal from a wafer surface by steam-water mixed spray is essentially a peel-off process. - Derivation of Nonlinear Wave Equations for Ultrasound Beam in Nonuniform Bubbly Liquids
Tetsuya Kanagawa, Takeru Yano, Junya Kawahara, Kazumichi Kobayashi, Masao Watanabe, Shigeo Fujikawa
NONLINEAR ACOUSTICS: STATE-OF-THE-ART AND PERSPECTIVES (ISNA 19), 1474, 144, 147, AMER INST PHYSICS, 2012, [Peer-reviewed]
English, International conference proceedings, Weakly nonlinear propagation of diffracted ultrasound beams in a nonuniform bubbly liquid is theoretically studied based on the method of multiple scales with the set of scaling relations of some physical parameters. It is assumed that the spatial distribution of the number density of bubbles in an initial state at rest is a slowly varying function of space coordinates and the amplitude of its variation is small compared with a mean number density. As a result, a Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation with dispersion and nonuniform effects for a low frequency case and a nonlinear Schrodinger (NLS) equation with dissipation, diffraction, and nonuniform effects for a high frequency case, are derived from the basic equations of bubbly flows. - Resonant Gas Oscillation with Evaporation and Condensation
Masashi Inaba, Takeru Yano, Masao Watanabe, Kazumichi Kobayashi, Shigeo Fujikawa
NONLINEAR ACOUSTICS: STATE-OF-THE-ART AND PERSPECTIVES (ISNA 19), 1474, 80, 83, AMER INST PHYSICS, 2012, [Peer-reviewed]
English, International conference proceedings, Resonant gas oscillation in a closed tube bounded by an oscillating plate and a vapor-liquid interface is theoretically analyzed by applying the asymptotic theory to the ES-BGK Boltzmann equation for the case of M-2 similar or equal to Kn << 1 and a small evaporation coefficient alpha = O(Kn), where M and Kn are the typical Mach number and the Knudsen number, respectively. As a result, we derive a nonlinear integro-differential equation for determining the wave profile with the evaporation and condensation in the form including alpha. - Numerical Analysis of Vapor-Liquid Two-Phase System Based on the Enskog-Vlasov Equation
Kazumichi Kobayashi, Kotaro Ohashi, Masao Watanabe
28TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS 2012, VOLS. 1 AND 2, 1501, 1145, 1151, AMER INST PHYSICS, 2012, [Peer-reviewed]
English, International conference proceedings, In this study, equilibrium and nonequilibrium numerical simulations for vapor-liquid two-phase systems were performed by using the Enskog-Vlasov equation. The kinetic boundary condition (KBC) at the interface was investigated. The simulation results showed that at a low or slightly high liquid temperature, the velocity distribution of the KBC obtained by our simulation is anisotropic Gaussian; this result agrees qualitatively with the results of the MD simulation performed by Ishiyama et al. (PRL, 2005). Also, the nonequilibrium nature of KBC becomes larger with the increase of liquid temperature. - Nonlinear Resonant Gas Oscillation Accompanied with Evaporation and Condensation
Masashi Inaba, Takeru Yano, Kazumichi Kobayashi, Masao Watanabe
28TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS 2012, VOLS. 1 AND 2, 1501, 53, 58, AMER INST PHYSICS, 2012, [Peer-reviewed]
English, International conference proceedings, Resonant gas oscillation in a closed tube bounded by an oscillating plate and a vapor-liquid interface is theoretically analyzed by applying the asymptotic theory to the ES-BGK Boltzmann equation for the case of M-P similar to Kn << 1 and a small evaporation coefficient alpha = O(root Kn), where M-P and Kn are the Mach number of the plate and the Knudsen number, respectively. As a result, we derive a nonlinear integro-differential equation for determining the wave profile with the evaporation and condensation including alpha. We numerically solve the integro-differential equation with the method of Fourier series, and obtain a parameter plane for shock formation conditions and also the prediction of critical condition for shock formation. - ジェット洗浄技術の最前線 水蒸気と水の混合噴流による洗浄技術
真田俊之, 渡部正夫, 関映子, 林田充司
砥粒加工学会誌, 55, 11, 640-643, 643, 砥粒加工学会, 01 Nov. 2011
Japanese - A cleaning technique by steam and water mixed spray
SANADA Toshiyuki, WATANABE Masao, SEKI Akiko, HAYASHIDA Atsushi
砥粒加工学会誌 = Journal of the Japan Society of Grinding Engineers, 55, 11, 640, 643, 砥粒加工学会, 01 Nov. 2011
Japanese - Nonlinear Wave Equations for Pressure Wave Propagation in Liquids Containing Gas Bubbles ( Comparison between Two-Fluid Model and Mixture Model )
Tetsuya Kanagawa, Masao Watanabe, Takeru Yano, Shigeo Fujikawa
Journal of Fluid Science and Technology, 6, 6, 838, 850, The Japan Society of Mechanical Engineers, Aug. 2011, [Peer-reviewed]
English, Scientific journal, Based on the unified theory by the present authors (Kanagawa et al., J. Fluid Sci. Tech., 5, 2010), the Korteweg-de Vries-Burgers (KdVB) equation and the nonlinear Schrödinger (NLS) equation with an attenuation term for weakly nonlinear waves in bubbly liquids are re-derived from a system of bubble-liquid mixture model equations composed of the conservation equations of mass and momentum, the Keller equation for bubble dynamics, and supplementary equations. We show that the re-derived KdVB equation and NLS equation are essentially the same as those derived from a system of two-fluid model equations except for the coefficients of nonlinear, dissipation, and dispersion terms. The differences in these coefficients are studied in detail, and we find that for the case of KdVB equation, the mixture model is valid only for sufficiently small initial void fractions. On the other hand, for the case of NLS equation, the range of validity of the mixture model depends on not only the initial void fraction but also the wavenumber concerned. - 気泡後部トロイダル渦の抗力への寄与
城田農, 佐藤文香, 真田俊之, 渡部正夫
混相流, 24, 5, 531, 537, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, 15 Mar. 2011
Japanese, Droplet impacts on solid surfaces are key elements in technical applications, such as semiconductor cleaning, rapid spray cooling and ink-jet printing. There exist varieties of physical parameters proposed that control the droplet impact although they are not thoroughly explored; hence, dynamics of the droplet after the impact are yet fully understood. In this study, we experimentally observed the high-speed droplet impact on acrylic surfaces in a vacuum chamber with a high-speed photography, in order to clarify the effects of both the ambient gas pressure around the droplet and the impact velocity. The results show that the splash does not occur under the reduced ambient gas pressure even when the impact velocity becomes much higher than in the conventional experiments, in the range of the present experimental conditions. - Experimental Estimate of Physical Actions of Steam-Water Mixer Spray : Dry-Etch Residue Removal, Resist Lift-Off, and Metal Erosion
MASHIKO Takashi, SANADA Toshiyuki, HASHIMOTO Kentaro, HORIBE Hideo, HAYASHIDA Atsushi, WATANABE Masao
Japanese journal of multiphase flow, 24, 5, 703, 709, 日本混相流学会, 15 Mar. 2011
Japanese - Contribution of a Toroidal Vortex behind a Bubble to Drag
SHIROTA Minori, SATO Ayaka, SANADA Toshiyuki, WATANABE Masao
Japanese journal of multiphase flow, 24, 5, 531, 537, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, 15 Mar. 2011
Japanese, Droplet impacts on solid surfaces are key elements in technical applications, such as semiconductor cleaning, rapid spray cooling and ink-jet printing. There exist varieties of physical parameters proposed that control the droplet impact although they are not thoroughly explored; hence, dynamics of the droplet after the impact are yet fully understood. In this study, we experimentally observed the high-speed droplet impact on acrylic surfaces in a vacuum chamber with a high-speed photography, in order to clarify the effects of both the ambient gas pressure around the droplet and the impact velocity. The results show that the splash does not occur under the reduced ambient gas pressure even when the impact velocity becomes much higher than in the conventional experiments, in the range of the present experimental conditions. - 微小液滴・微小気泡・界面張力[3‐1]ナノ液滴と蒸気の一成分気液二相系における平衡条件の検討
YAGUCHI HISAO, FUJIKAWA SHIGEO, YANO TAKERU, WATANABE MASAO
アンサンブル, 13, 1, 7, 11, 分子シミュレーション研究会, 31 Jan. 2011
Japanese - Nonlinear Wave Equation for Ultrasound Beam in Nonuniform Bubbly Liquids
KANAGAWA Tetsuya, YANO Takeru, WATANABE Masao, FUJIKAWA Shigeo
JFST, 6, 2, 279, 290, The Japan Society of Mechanical Engineers, 2011
English, In our previous paper (Kanagawa et al., J. Fluid Sci. Tech., 5, 2010), we have proposed a systematic method for derivation of various types of nonlinear wave equations for plane waves in bubbly liquids. The method makes use of an asymptotic expansion with multiple scales in terms of a small wave amplitude as an expansion parameter and a set of scaling relations of physical parameters, based on basic equations of two-fluid model of bubbly flows. In this paper, we extend the method so as to handle a weakly diffracted ultrasound beam in a quiescent liquid containing a number of spherical gas bubbles distributed with a weak nonuniformity. Because of the high expandability of the original method, the extension can be accomplished by adding a scaling relation of the diameter of the beam to the original set of scaling relations. As a result, we derive a generalized Khokhlov—Zabolotskaya—Kuznetsov (KZK) equation [or a generalized Kadomtsev—Petviashvili (KP) equation] for a long wave and low frequency case. - 8I-11 Material transport and tissue development in engineered cartilage model culture under cyclic compression
SAWAE Yoshinori, WATANABE Masao, OMATA Seiji, MURAKAMI Teruo
The Proceedings of the Bioengineering Conference Annual Meeting of BED/JSME, 2010, 0, 181, 182, The Japan Society of Mechanical Engineers, 2011, [Peer-reviewed]
Japanese - High-Speed Droplet Impact as an Elementary Process of Physical Cleaning
T. Fujikawa, Y. Tatekura, K. Kobayashi, T. Sanada, A. Hayashida, M. Watanabe
SEMICONDUCTOR CLEANING SCIENCE AND TECHNOLOGY 12 (SCST 12), 41, 5, 67, 74, ELECTROCHEMICAL SOC INC, 2011
English, International conference proceedings, In the steam-water mixed spray-cleaning technique, droplet impact on the solid surface is the one of the primarily important physical processes. We experimentally studied a droplet impact on a solid place that moves with a speed ranging from 1 to 50 m/s using high-speed video camera. We observed that high-speed liquid film flows radially outward along the surface just after the impact. In addition, we also observed that liquid turns into corona splash in the cases of higher impact velocities. These flows with large velocities can generate huge shear stress on the solid surface, which may contribute to cleaning. Furthermore, we numerically studied the velocity field development and found that gas flow field may also contribute in advecting removed particles or stripped resists away from the original place. - Modeling of bouncing of a single clean bubble on a free surface
A. Sato, M. Shirota, T. Sanada, M. Watanabe
PHYSICS OF FLUIDS, 23, 1, 013307, AMER INST PHYSICS, Jan. 2011, [Peer-reviewed]
English, Scientific journal, Bouncing of a rectilinearly rising bubble on a free surface is modeled with the use of a simple mass-spring system. The most striking characteristic of the present model is that it is based on an equation of motion of the system that consists of two springs connected in series; hence, we can account for the restoring forces of both the bubble and free surfaces. This equation of motion is coupled with a conservation equation of energy that is taking into account an exchange between the surface energy due to deformations of both the bubble and free surfaces and the kinetic energy of the bubble. With the use of these equations, the contact time, i.e., the time duration of a bubble contacting a free surface, is determined to be a half of the characteristic period of the oscillator. We also conducted experiments of a single clean bubble in ultrapure water bouncing on a flat free surface in order to verify the present model. We found that results obtained from the model agree well with the experimentally obtained results, even in cases with significant surface deformations. When bubbles are smaller than 0.6 mm in radius, the deformations of both the bubble and free surfaces play important roles in bouncing. In case of larger bubbles, on the other hand, bouncing is dominated by the free surface deformation since the bubble has already been highly deformed before collision. We conclude that bouncing of a bubble on a free surface can be explained clearly by the present model based on a simple mass-spring system. (c) 2011 American Institute of Physics. [doi:10.1063/1.3546019] - 水蒸気と水の混合噴流による表面洗浄技術 物理力による表面薄膜剥離
MASHIKO TAKASHI, SANADA TOSHIYUKI, WATANABE MASAO, HAYASHIDA ATSUSHI, SEKI AKIKO
クリーンテクノロジー, 20, 8, 65, 69, 10 Aug. 2010
Japanese - 気泡流中の弱非線形波動 (非線形波動現象の数理と応用)
金川 哲也, 矢野 猛, 渡部 正夫, 藤川 重雄
数理解析研究所講究録, 1701, 40, 46, 京都大学, Aug. 2010
Japanese - Unified Theory Based on Parameter Scaling for Derivation of Nonlinear Wave Equations in Bubbly Liquids
Tetsuya KANAGAW, Takeru YANO, Masao WATANABE, Shigeo FUJIKAWA
Journal of Fluid Science and Technology, 5, 3, 351, 369, The Japan Society of Mechanical Engineers, Jul. 2010, [Peer-reviewed]
English, Scientific journal, We propose a systematic derivation method of the Korteweg-de Vries-Burgers (KdVB) equation and nonlinear Schrödinger (NLS) equation for nonlinear waves in bubbly liquids on the basis of appropriate choices of scaling relations of physical parameters. The basic equations are composed of a set of conservation equations for mass and momentum and the equation of bubble dynamics in a two-fluid model. The scaling of parameters is related to the wavelength, frequency, propagation speed, and amplitude of waves concerned. With the help of the method of multiple scales, appropriate choices of the parameter scaling allow us to derive various nonlinear wave equations systematically from a set of basic equations. The result shows that the one-dimensional nonlinear propagation of a long wave with a low frequency is described by the KdVB equation, and that of an envelope of a carrier wave with a high frequency by the NLS equation. Thus, we establish a unified theory of derivation of nonlinear wave equations in bubbly liquids. - The Sound Wave Method for Measurement of Evaporation Coefficient
Shigeto NAKAMURA, Takeru YANO, Masao WATANABE, Shigeo FUJIKAWA
Journal of Fluid Science and Technology, 5, 1, 26, 34, The Japan Society of Mechanical Engineers, Feb. 2010, [Peer-reviewed]
English, Scientific journal, A new method for measurement of evaporation coefficient using sound resonance experiment is proposed on the basis of a theory of molecular gas dynamics, by which the evaporation coefficient is expressed as a function of the amplitude of standing sound wave between a planar sound source and a vapor-liquid interface facing against it. To demonstrate the applicability of this method, we carried out test experiments under the condition of neither evaporation nor condensation for several initial pressures, 30, 50, 80 and 101 kPa, at room temperature. In the experiments, we measure the amplitude of standing wave with a resonant frequency generated in a cylindrical space filled with air and closed by liquid water. We utilize the second harmonics component excited by the nonlinearity of sound to determine the evaporation coefficient, thereby eliminating the electromagnetic noises from measured signals. We find that the amplitude of the second harmonics at sound resonance decreases with the decrease in the initial pressure. - Single Rising Bubble Motion in Aqueous Solution of Electrolyte
Ayaka SATO, Masumi AOKI, Masao WATANABE
Journal of Fluid Science and Technology, 5, 1, 14, 25, The Japan Society of Mechanical Engineers, Feb. 2010, [Peer-reviewed]
English, Scientific journal, Effects of electrolytes on bubble coalescence are investigated experimentally from fluid dynamic point of view. Collisions of a bubble with free surface in two kinds of liquids, namely, ultrapure water and sodium chloride solution, are observed using a high speed camera. It is found that the repetitive number of bubble bounces on a free surface in electrolyte solution is larger than that in ultrapure water when the equivalent bubble radii are the same. This result qualitatively shows that electrolyte works to prevent bubbles from coalescing. It is also revealed that the bubbles can coalesce if their Weber numbers, which are based on the radius of curvature of the front side of the bubble and the approach velocity just before the collision with the free surface, are less than a critical Weber number. Furthermore, the critical Weber number decreases with the increase in the concentration of the electrolyte solutions despite the fluid dynamic characteristics, such as bubble rise velocity and bubble shape, are not affected by the addition of the electrolytes. It is concluded that Weber number is the most important parameter to specify the effects of electrolytes on bubble coalescence. - Chemical-free cleaning process, steam and water mixed spray
SANADA TOSHIYUKI, WATANABE MASAO, MASHIKO TAKASHI, HAYASHIDA ATSUSHI, KOMANO HIDEO
空気清浄, 47, 5, 31, 36, 日本空気清浄協会, 31 Jan. 2010
Japanese - S0507-1-2 Shock-Tube-Deduced Condensation Coefficients of Water and Methanol Vapors near Equilibrium States : Boltzmann-Equation-Assisted Data Analysis
MOURI Shingo, OGASAWARA Toshiki, YAGUCHI Hisao, WATANABE Masao, FUJIKAWA Shigeo
The proceedings of the JSME annual meeting, 2010, 239, 240, The Japan Society of Mechanical Engineers, 2010
Japanese, The condensation coefficients of water and methanol, i.e., the ratios of condensation mass flux of vapor molecules to their mass flux colliding on the interface, are evaluated by combining the experiment conducted by a shock tube and the numerical simulation of Gaussian-BGK Boltzmann equation applicable to polyatomic gases. Film condensation occurs on the endwall of vapor filled shock-tube, when a shock wave is reflected at the endwall and the vapor eventually becomes supersaturated there. The formed liquid film grows with the lapse of time. The time evolution in thickness of the liquid film is measured by an optical interferometer, and thereby the growth rate of the film is obtained. The rate is incorporated into the kinetic boundary condition at the interface for the Gaussian-BGK Boltzmann equation, the solution of which is in consequence obtained uniquely. The condensation coefficients in nearequilibrium states for water and methanol are found to be close to those evaluated by molecular dynamics simulations at equilibrium states. - S0507-1-1 Nonequilibrium Molecular Dynamics Simulation of Evaporation and Condensation of Nanodroplet
YAGUCHI Hisao, YANO Takeru, WATAnABE Masao, FUJIKAWA Shigeo
The proceedings of the JSME annual meeting, 2010, 237, 238, The Japan Society of Mechanical Engineers, 2010
Japanese, Nonequilibrium molecular dynamics simulation is carried out to study weak condensation of argon vapor into its nanodroplet. Temperature of the nanodroplet is kept at 90 K by using the velocity scaling method. The nanodroplet grows steadily ranging from about 3.3 to 3.4 nm in the radius R_m which is defined as the radius of the center of transition layer in density profile. The mass fluxes at the vapor-nanodroplet interface are investigated and condensation coefficient of the nanodroplet is successfully determined. As a result, the condensation coefficient is almost equal to the evaporation coefficient obtained by our previous study. The rate of change of R_m can be predicted by the mass fluxes and evaporation/condensation coefficients within about 16 percent error. - Molecular Dynamics Study of Vapor-liquid Equilibrium Condition for Nanodroplet
Hisao Yaguchi, Takeru Yano, Masao Watanabe, Shigeo Fujikawa
Proceedings of 7th International Conference on Multiphase Flow, 2010, [Peer-reviewed] - Nonlinear wave equations for pressure wave propagation in liquids containing gas bubbles (comparison between two-fluid model and mixture model)
Tetsuya Kanagawa, Masao Watanabe, Takeru Yano, Shigeo Fujikawa
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 76, 771, 1802, 1810, Japan Society of Mechanical Engineers, 2010
Japanese, Scientific journal, Based on the unified theory by the present authors (T. Kanagawa, et al., J. Fluid Sci. Tech., 5, 2010), the Korteweg-de Vries-Burgers (KdVB) equation and the nonlinear Schrödinger (NLS) equation with an attenuation term for weakly nonlinear waves in bubbly liquids are re-derived from a system of bubble-liquid mixture model equations composed of the conservation equations of mass and momentum, the Keller equation for bubble dynamics, and supplementary equations. We show that the re-derived KdVB equation and NLS equation are essentially the same as those derived from a system of two-fluid model equations except for the coefficients of nonlinear, dissipation, and dispersion terms. The differences in these coefficients are studied in detail, and we find that for the case of KdVB equation, the mixture model is valid only for sufficiently small initial void fractions. On the other hand, for the case of NLS equation, the range of validity of the mixture model depends on not only the initial void fraction but also the wavenumber concerned. - Nonlinear wave equations for pressure wave propagation in liquids containing gas bubbles (comparison between two-fluid model and mixture model)
Tetsuya Kanagawa, Masao Watanabe, Takeru Yano, Shigeo Fujikawa
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 76, 771, 1802, 1810, Japan Society of Mechanical Engineers, 2010
Japanese, Scientific journal, Based on the unified theory by the present authors (T. Kanagawa, et al., J. Fluid Sci. Tech., 5, 2010), the Korteweg-de Vries-Burgers (KdVB) equation and the nonlinear Schrödinger (NLS) equation with an attenuation term for weakly nonlinear waves in bubbly liquids are re-derived from a system of bubble-liquid mixture model equations composed of the conservation equations of mass and momentum, the Keller equation for bubble dynamics, and supplementary equations. We show that the re-derived KdVB equation and NLS equation are essentially the same as those derived from a system of two-fluid model equations except for the coefficients of nonlinear, dissipation, and dispersion terms. The differences in these coefficients are studied in detail, and we find that for the case of KdVB equation, the mixture model is valid only for sufficiently small initial void fractions. On the other hand, for the case of NLS equation, the range of validity of the mixture model depends on not only the initial void fraction but also the wavenumber concerned. - Effects of Electrolytes on Bubble Coalescence
Ayaka SATO, Masumi AOKI, Masao WATANABE
Progress in Multiphase Flow Research, 4, 103, 110, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, Dec. 2009, [Peer-reviewed]
Japanese, Scientific journal, Effects of electrolytes on bubble coalescence are investigated experimentally. Collisions of bubbles with free surface of three kinds of liquids, namely, super purified water, NaCl solution and KCl solution, are observed by using a high speed camera. It is found that the numbers of bounces on a free surface in electrolyte solution are larger than those in super purified water with the same equivalent bubble radius. This result qualitatively indicates that electrolyte works to prevent bubbles from coalescing. It is also revealed that a bubble can coalesce if the Weber number, which is based on radius of curvature of fore side of the bubble and approach velocity just before collision with free surface, is less than a critical value. The decrease of the critical Weber number, which corresponds to the inhibition of the coalescence, is observed with the increase in the concentration of the electrolyte solutions. - Motion and coalescence of a pair of bubbles rising side by side
Toshiyuki Sanada, Ayaka Sato, Minori Shirota, Masao Watanabe
CHEMICAL ENGINEERING SCIENCE, 64, 11, 2659, 2671, PERGAMON-ELSEVIER SCIENCE LTD, Jun. 2009, [Peer-reviewed]
English, Scientific journal, Bouncing and coalescence of a pair of slightly deformed bubbles rising side by side in a quiescent liquid are experimentally studied. The trajectories and shapes of the bubbles are investigated in detail by using a high-speed video camera. The wakes of bubbles are visualized by using a photochromic dye that is colored with UV light irradiation. We observe that the patterns of the trajectories of rising bubbles are strongly dependent on the Reynolds number. When the Reynolds number is over the critical region, two bubbles approach each other and then collide. After the collision, two types of motions are observed-coalescence and bouncing. We investigate the critical Reynolds number and Weber number over which the bubbles bounce. In the definitions of these numbers, we use vertical velocity, instead of horizontal one, as the characteristic velocity. We clarify that the critical Weber number is around 2 regardless of the Morton number. The critical Reynolds number decreases with an increase in the Morton number. Moreover, the visualization of the wake of bubbles enables us to observe the vortex separation from the rear surface of the bubbles on collision. We find that the vortex separation from the rear of bouncing bubbles causes a decrease in the rising velocity and an increase in the horizontal speed after their collision. We also observe that the behavior of repeatedly bouncing bubbles is significantly influenced by the wake instability of a single bubble rather than by the bubble-bubble interaction. By applying an existing model for spherical bubble-bubble interaction, we clarify that the revised model accurately describes the trajectory of a pair of slightly deformed bubbles using the restitution coefficient and velocity fluctuation from the experimental results. (C) 2009 Elsevier Ltd. All rights reserved. - Removal of post-dry etch residue using ultra low environmental load technique
A. Hayashida, A. Seki, T. Mashiko, T. Sanada, M. Watanabe
ECS Transactions, 25, 5, 249, 256, Electrochemical Society Inc., 2009
English, International conference proceedings, A novel ultra low environmental load removal technique of post-dry etch residue is developed, by applying physical force cleaning technique using high-speed steam-water mixture spray. It is found that the removal rate of the proposed technique depends on the dry-etch processes, and that the steam-water mixture spray almost completely removes the post-dry etch residue from some kinds of dry etched wafers without help of any chemicals. It is also found that the proposed technique requires very dilute concentration of inorganic solution, if necessary, to remove post-dry etch residue completely from other kinds of wafers and that removal process using amine compound with isopropyl alcohol is unnecessary. By contrast, air-water mixture spray could not remove the dry-etch residue at all even with some chemicals. Therefore it is understood that steam atmosphere significantly contributes the proposed technique. The characteristic feature and efficiency of the proposed technique are discussed. - J0201-1-6 Acoustic Characteristics of Ultrasound Propagating in Liquid Containing Lipid Bubbles
IMAI Ryosuke, NAKAGAWA Hiroya, SAKURAI Kousuke, WATANABE Masao, FUJIKAWA Shigeo
The proceedings of the JSME annual meeting, 2009, 107, 108, The Japan Society of Mechanical Engineers, 2009
Japanese, In the field of medical engineering, the application of bubbles of nanometer size to Drug Delivery System (DDS) has attracted great attention as the administration of next generation. DDS with bubbles is expected to be a noninvasive clinical treatment. As the transport carrier of DDS, there exists bubble encapsulated in a lipid bilayer, generally called as a lipid bubble. However, dynamic properties of these lipid bubbles are not yet made clear. In this study, acoustic characteristics of lipid bubbles are experimentally investigated. The resonant frequencies of lipid bubbles are evaluated from attenuation of ultrasound pulse propagating through the experimental cell filled with lipid bubble solution. It is found that the attenuation spectrum has two dominant peaks in the frequency range of 1.0 through 14.0 MHz due to the acoustic energy absorbed by lipid bubble with resonant oscillations. - T0501-2-5 Molecular Dynamics Analysis of Temperature Change in Nanodroplet Evaporating into Vacuum
YAGUCHI Hisao, TANAKA Ryoichi, YANO Takeru, WATANABE Masao, FUJIKAWA Shigeo
The proceedings of the JSME annual meeting, 2009, 115, 116, The Japan Society of Mechanical Engineers, 2009
Japanese, Molecular dynamics simulations of an argon nanodroplet evaporating into vacuum are carried out to investigate time development of its temperature. Configuration in vaporliquid equilibrium state of the nanodroplet with 3.6 nm in radius at 105 K is adopted as initial configuration of the evaporation. Although the temperature of nanodroplet decreases with time because of the loss of latent heat for evaporation, rapid temperature rise has been observed at about 8.0 ns. Radial distribution function of molecules inside the nanodroplet suggests that phase change from liquid to solid has been occurred. Recovery from the supercooling consequent to release of latent heat for solidification is thought to be cause of this rapid temperature rise. - T0501-2-4 Evaluation of Condensation Coefficient of Water in Near-equilibrium State by Shock Tube and Molecular Gas Dynamics
OGASAWARA Toshiki, YAMANO Daigo, WATANABE Masao, FUJIKAWA Shigeo
The proceedings of the JSME annual meeting, 2009, 113, 114, The Japan Society of Mechanical Engineers, 2009
Japanese, The condensation coefficient of water, ie., the ratio of condensation mass flux of vapor molecules to incoming mass flux at the interface, is evaluated by combining the experiment conducted by a shock tube and the numerical simulation of Gaussian-BGK Boltzmann equation applicable to polyatomic gases. Film condensation occurs on the endwall of a vaporfilled shock-tube, when a shock wave is reflected at the endwall and the vapor becomes supersaturated there. The formed liquid film grows with the lapse of time. The time evolution in thickness of the liquid film is measured by an optical interferometer, and thereby the growth rate of the film is obtained. The rate is incorporated into the kinetic boundary condition at the interface for the Gaussian-BGK Boltzmann equation, and the unique numerical solution of the vaporliquid system is obtained. Values of condensation coefficient in near equilibrium state are found to be close to that evaluated by molecular dynamics simulations at the equilibrium state. - Impact of steam-water mixed spray on silicon and metal surfaces
T. Mashiko, A. Hayashida, Y. Yamada, T. Sanada, M. Watanabe
ECS Transactions, 25, 5, 233, 240, 2009, [Peer-reviewed]
English, International conference proceedings, Performance of photoresist stripping using steam-water mixed spray is quantitatively investigated with water flow rate as the operating parameter. The most striking and the most important finding is that air-water mixed spray turns out hardly effective. This result shows the peculiar superiority of the proposed technique. As we found that the prominently excessive long time of spraying of steam-water mixture on metal surface results in surface abrasion, this result strongly suggests that both the resist stripping and metal surface abrasion are dominated by essentially the same mechanism. We speculate that our proposing technique is categorized in the physical force cleaning. We discuss the role of the water flow rate in this cleaning technique and the validity of the assumption of physical force cleaning. - Post Ion-Implant Photoresist Stripping Using Steam and Water: Pre-treatment in a steam atmosphere and steam-water mixed spray
Toshiyuki Sanada, Masao Watanabe, Atsushi Hayashida, Yoichi Isago
ULTRA CLEAN PROCESSING OF SEMICONDUCTOR SURFACES IX, 145-146, 273, +, TRANS TECH PUBLICATIONS LTD, 2009, [Peer-reviewed]
English, International conference proceedings - Cleaning Technique Using High-Speed Steam-Water Mixed Spray
Masao Watanabe, Toshiyuki Sanada, Atsushi Hayashida, Yoichi Isago
ULTRA CLEAN PROCESSING OF SEMICONDUCTOR SURFACES IX, 145-146, 43, +, TRANS TECH PUBLICATIONS LTD, 2009, [Peer-reviewed]
English, International conference proceedings - Post ion-implant photoresist stripping using steam and water: Pre-treatment in a steam atmosphere and steam-water mixed spray
Toshiyuki Sanada, Masao Watanabe, Atsushi Hayashida, Yoichi Isago
Solid State Phenomena, 145-146, 273, 276, Trans Tech Publications Ltd, 2009, [Peer-reviewed]
English, International conference proceedings, It is well-known that ion-implant doses greater than 5E14 atoms/cm 2 can create an amorphous carbon-like layer "crust", and also that this crust is extremely difficult to dissolve with wet chemicals. In practice, a combination of dry plasma ashing and wet chemical removal is used to eliminate the photoresist. In this study, a novel photoresist stripping technique is proposed. We have improved wet vapor photoresist stripping technique [1] using the mixture of high-speed steam flow and purified water droplets. Relatively low pressure clean steam is mixed with purified water in the nozzle, and sprayed on a photoresist coated Si wafer. We have also developed a pre-treatment method in a chamber with keeping both temperature and humidity constant, in order to strip post ion-implanted photoresit. The most significant feature of this proposed technique is that we use water only
hence we are able to strip photoresist without chemicals. © (2009) Trans Tech Publications. - Image-based CFD on the Hepatic Portion of the Inferior Vena Cava on Budd-Chiari Syndrome.
MATSUBARA MIZUHO, WATANABE MASAO
日本臨床バイオメカニクス学会誌, 29, 99, 106, 01 Nov. 2008
Japanese - Numerial Analysis on High-Speed Droplet Impact on a Solid Surface : Study on Cavitation Inception(Fluids Engineering)
WATANABE Masao, SANADA Toshiyuki, YAMASE Masao
Transactions of the Japan Society of Mechanical Engineers. B, 74, 744, 1717, 1724, 一般社団法人日本機械学会, 25 Aug. 2008
Japanese, Our experimental results [T. Sanada, et. al., ASME-FEDSM 2007-37129] showed that spraying relatively low pressure stream (0.1MPa-0.2MPa), mixed with super-purified water in the nozzle, on a solid surface, caused harsh erosion. We turned our attention to the occurrence of a strong focused rarefaction wave in the middle of the droplet, possibly cavitation. Experimental results that the degrees of the erosion are heavily dependent on temperature also may support the existence of cavitation. We numerically studied the dynamics of high speed liquid droplet impacts on a solid surface by solving the Euler equation of gas-liquid two phase compressible flow. We discuss the possibility of cavitation as the primary cause of the experimentally observed harsh erosion on the solid surface. - Numerial Analysis on High-Speed Droplet Impact on a Solid Surface (Study on Cavitation Inception)
WATANABE MASAO, SANADA TOSHIYUKI, YAMASE MASAO
日本機械学会論文集 B編, 74, 744, 1717, 1724, The Japan Society of Mechanical Engineers, 25 Aug. 2008
Japanese, Our experimental results [T. Sanada, et. al., ASME-FEDSM 2007-37129] showed that spraying relatively low pressure stream (0.1MPa-0.2MPa), mixed with super-purified water in the nozzle, on a solid surface, caused harsh erosion. We turned our attention to the occurrence of a strong focused rarefaction wave in the middle of the droplet, possibly cavitation. Experimental results that the degrees of the erosion are heavily dependent on temperature also may support the existence of cavitation. We numerically studied the dynamics of high speed liquid droplet impacts on a solid surface by solving the Euler equation of gas-liquid two phase compressible flow. We discuss the possibility of cavitation as the primary cause of the experimentally observed harsh erosion on the solid surface. - Motion and drag of a single bubble in super-purified water
Toshiyuki Sanada, Keiji Sugihara, Minori Shirota, Masao Watanabe
Fluid Dynamics Research, 40, 7-8, 534, 545, Jul. 2008
English, Scientific journal, We experimentally study the motion and shape of a single rising bubble in super-purified water. We develop an apparatus that is equipped with a measurement system for monitoring both the resistivity and amount of total organic carbon of water in order to evaluate the purity of water. We investigate the critical Reynolds number above which the rising bubble motion changes from rectilinear to zigzag or spiral motion. It is revealed that the critical Reynolds number is susceptible to the range of observation height in the experimental tank. Next, we investigate the effects of the amount of contaminant on bubble motion. The drag coefficient of bubbles in the case of low Reynolds numbers is greatly affected by a small amount of contaminant. We also compare the experimental results of both the terminal rising velocity and drag coefficient with theoretical results for ellipsoidal bubble obtained for high Reynolds number. For smaller bubbles, good agreement is found between the experimental and theoretical results. For larger bubbles, however, discrepancies are prominent. Finally, we examine the effects of the bubble shape on its motion. There exist significant discrepancies between the experimental and theoretical results of aspect ratio as a function of Weber number, even in the range where the experimental and theoretical results in both the terminal velocity and drag coefficient show good agreement. © 2008 The Japan Society of Fluid Mechanics and Elsevier B.V. - 単一気泡の形状と定常抗力
SATO AYAKA, SHIROTA MINORI, SANADA TOSHIYUKI, WATANABE MASAO
混相流研究の進展, 3, 2008, 35, 41, THE JAPANESE SOCIETY FOR MULTIPHASE FLOW, 15 Jun. 2008
Japanese, Relations between drag coefficients CD and bubble shapes are investigated by comparing our experimental results with both analytical [Moore, J. Fluid Mech., 23, 749-766 (1965)] and numerical results [Blanco & Magnaudet, Phys. Fluids, 7(6), 1265-1274(1995)] on ellipsoidal bubbles rising in a quiescent clean liquid. We clarify that the analytically obtained CD overestimates the experimental results especially in the case of either high aspect ratio or low Reynolds number, and that numerically obtained results for ellipsoidal bubbles well predict our experimental results. We also show that the effect of the deviation in the shape from the ellipsoid, i.e., fore-aft asymmetry, on CD is negligible; CD for fore-aft asymmetry bubbles is in good agreement with the numerically obtained CD for ellipsoidal bubbles. - Formation of a submillimeter bubble from an orifice using pulsed acoustic pressure waves in gas phase
Minori Shirota, Toshiyuki Sanada, Ayaka Sato, Masao Watanabe
PHYSICS OF FLUIDS, 20, 4, 043301, AMER INST PHYSICS, Apr. 2008, [Peer-reviewed]
English, Scientific journal, The mechanism of a bubble production method using pulsed acoustic pressure waves in gas phase is investigated using high-speed photography. The acoustic characteristics of the present bubble generator are also investigated. We found out the optimal acoustic waveform for producing only one bubble per one action; the bubble detachment radius is accurately controlled by first applying the positive onset-assistance acoustic pressure wave and then the negative detachment-assistance acoustic pressure wave with an accurately controlled time lapse. From an orifice with a radius of 0.09 mm submerged in water, bubbles with radii in the range of 0.28-0.78 mm with an extremely small standard deviation of less than 1 mu m are obtained. The shrinking and pinch-off motions of a capillary bridge connecting the bubble and orifice at the time of bubble detachment are observed in detail. The balancing force on a growing bubble, which is based on a spherical bubble formation model is also estimated. As a result, we reveal that when the gas pressure is decreased due to a negative pressure wave, the capillary bridge submerges into the orifice and an upward added mass force is applied on the bubble, both of which cause the detachment of the bubble from the orifice. (C) 2008 American Institute of Physics. - Development of Cleaning Technique by Using Spray Mixed with Steam and Water
SANADA TOSHIYUKI, SAITO TAKAYUKI, HAYASHIDA ATSUSHI, SAITO TERUO, YAMASE MASAO, WATANABE MASAO
噴流工学, 24, 3, 4-10, 18 Jan. 2008
Japanese - 703 Evaluation of Red Blood Cell Dynamics with High Speed Digital Video Capillaroscopy
NAKAMURA Yuuki, WATANABE Masao, IRIBE Masaki, MATSUBARA Mizuho
The proceedings of the JSME annual meeting, 2008, 21, 22, The Japan Society of Mechanical Engineers, 2008
Japanese, Nailfold video capillaroscopy (NVC) can observe the micro vascular structure non-invasively. We developed NVC by using high speed digital video camera to evaluate both micro vascular structure and red blood cell movement quantitatively The objects of this study are to evaluate the radius distribution of micro vascular by level-set method and also the red blood cell velocity by tracing plasma gap between blood cells. - 337 Advection and Diffusion Transport Phenomena in Engineered Cartilage
NOBAYASHI Makoto, KITAJIMA Yousuke, WATANABE Shouhei, SAWAE Yoshinori, WATANABE Masao
The proceedings of the JSME annual meeting, 2008, 73, 74, The Japan Society of Mechanical Engineers, 2008
Japanese, Engineered cartilages are expected to be used for the treatment of cartilage defects. Cartilage tissue is avascular; hence transport phenomena are controlled by diffusion and also advection by so called "pumping mechanism" of tissue. The objective of present paper is to evaluate the contribution of both diffusion and advection in engineered tissue for the control of transport phenomena. - Motion and drag of single bubbles in super-purified water
Toshiyuki Sanada, Keiji Sugihara, Minori Shirota, Masao Watanabe
FLUID DYNAMICS RESEARCH, 40, 534, 545, Jan. 2008, [Peer-reviewed] - Impact of High-speed steam-droplet spray on solid surface
Toshiyuki Sanada, Masao Watanabe, Minori Shirota, Masao Yamase, Takayuki Saito
FLUID DYNAMICS RESEARCH, 40, 627, 636, Jan. 2008, [Peer-reviewed] - Bubble wake visualization by using photochromic dye
Toshiyuki Sanada, Minori Shirota, Masao Watanabe
CHEMICAL ENGINEERING SCIENCE, 62, 24, 7264, 7273, PERGAMON-ELSEVIER SCIENCE LTD, Dec. 2007, [Peer-reviewed]
English, Scientific journal, Wake structure of a single "clean bubble", rising in rectilinear, zigzagging or spiraling path, is experimentally investigated. A single nitrogen gas bubble was produced in a silicone oil pool and the wake structure development in the rear of the rising bubble was visualized by using photochromic dye. The flexibility of this visualization method enabled us to distinguish wake from drift easily. Both bubble motion and wake structure were recorded by using stereo high-speed video camera simultaneously. We present the first experimental support for the existence of the standing eddy at the rear of the clean bubble, as predicted by a previous numerical study by Ryskin and Leal [1984. Journal of Fluid Mechanics 148, 19-35], Dandy and Leal [1986. Physics of Fluids 29(5), 1360-1366] and Blanco and Magnaudet [1995. Physics of Fluids 7(6), 1265-1274]. We study motion of a pair of vortex filaments, which is called double-threaded type wake, in the case of bubble rising in an axi-asymmetric path. Visualization results of multiple formations of horse-shoe type vortices in one period of zigzag motion of rising bubble with shape oscillations, which has not been observed in previous studies are also presented. (C) 2007 Elsevier Ltd. All rights reserved. - Behavior of single rising bubbles in superpurified water
Keiji Sugihara, Toshiyuki Sanada, Minori Shirota, Masao Watanabe
KAGAKU KOGAKU RONBUNSHU, 33, 5, 402, 408, SOC CHEMICAL ENG JAPAN, Sep. 2007
Japanese, Scientific journal, We experimentally studied the motion and shape of single rising bubbles in superpurified water. We developed an apparatus, which was equipped with a measurement system of both resistance and TOC value of water, in order to maintain water purity by monitoring it during the experiment. We investigated the critical Reynolds number over which the rising bubble motion changed front rectilinear motion to zigzag or spiral motion. In the case of Re=650, the bubble reached the terminal velocity at the height of 40 mm and the onset of transition to zigzag or spiral motion was observed at the height of 140 mm. Oil the other hand, in the case of Re 700, both the terminal velocity and onset of transition were observed at the approximately same height; hence the critical Reynolds number was unable to be uniquely determined. The height of the onset of transition increased with the decrease in Reynolds number. We also compared experimental results of both the terminal rise velocities and drag coefficients with those obtained theoretically for ellipsoidal bubble in the limit of potential flow theory. For smaller bubbles, experimental values of the terminal velocities and drag coefficients showed good agreement with those obtained theoretically. For larger bubbles, however, the deferences between experimental and theoretical values in the terminal velocities and drag coefficients became prominent. Finally we quantitatively evaluated the bubble shapes by expanding them in terms of Legendre's polynomials and proposed the new correlations of the aspect ratio with either Weber number or Eotvos number. - フォトクロミック染料による気泡後部定在渦の可視化
SHIROTA MINORI, ONO TOMOKI, SUGIHARA KEIJI, SANADA TOSHIYUKI, WATANABE MASAO
混相流研究の進展, 2, 125, 132, 01 Apr. 2007
Japanese - Formation of Single Bubble of Sub-millimeter Size Using Pulsed Pressure Fluctuation of Gas
SHIROTA MINORI, SANADA TOSHIYUKI, ARATA YASUHIRO, WATANABE MASAO, KAMEDA MASAHARU
日本機械学会論文集 B編, 73, 726, 467, 473, The Japan Society of Mechanical Engineers, 25 Feb. 2007
Japanese, The mechanism of a bubble production method using controlled gas pressure fluctuation, originally developed by Kariyasaki and Osaka [Trans. JSME, Series B, Vol.68, No.674, (2002)1, is further investigated using high-speed photography. We found out more appropriate pressure fluctuation than that of Kariyasaki and Osaka in producing single bubble. The radius of bubbles can be varied from about 0.3 to 0.8 mm with extremely small standard deviation of less than 1μm. Shrinking motion of a capillary bridge connecting a bubble and a nozzle was observed in detail. Force balance on a growing bubble which is based on a spherical bubble formation model is also estimated. As a result, we reveal that when gas pressure is decreased the capillary bridge is sucked down into a nozzle and upward added mass force is applied on a bubble, both of which cause the detachment of a bubble from a nozzle. - No-slip Boundary Condition on Complex Geometry in Lattice Boltzmann Method (1st Report, Construction of Space-Time Bounce-Back Method)
WATANABE MASAO, SANADA TOSHIYUKI, SHIROTA MINORI, MATSUKUMA YOSUKE
日本機械学会論文集 B編, 73, 726, 459, 466, The Japan Society of Mechanical Engineers, 25 Feb. 2007
Japanese, A new treatment of no slip boundary condition on complex geometry in a lattice Boltzmann method is proposed. We developed Space-Time Bounce-Back (STBB) method, which evaluate distribution functions in the vicinity of the solid boundary whose geometry described in the scale less than the lattice size. The STBB method is based on not only the spatial distribution but also the temporal distribution of distribution functions, in order to satisfy both the complete reflection on the solid boundary and the second order accuracy in the spatial discretization. Two-dimensional channel flow is calculated by using the proposed method, and both the accuracy and the stability are examined by comparing with the analytical solution. - High Speed Digital Video Capillaroscopy: Nailfold Capillary Shape Analysis and Red Blood Cell Velocity Measurement
WATANABE Masao, MATSUBARA Mizuho, SANADA Toshiyuki, KURODA Hiroaki, IRIBE Masaki, FURUE Masutaka
JBSE, 2, 2, 81, 92, The Japan Society of Mechanical Engineers, 2007
English, Nailfold capillaroscopy has been shown to reflect microvascular disturbances mainly in connective tissue diseases, and the development of video capillaroscopy made it possible to determine capillary red blood cell velocity by measuring the displacement of plasma gaps between red cells. We improved both temporal and spatial resolutions of video capillaroscopy by developing the high speed digital video capillaroscopy, integrating high speed digital video camera, deep-focus zoom lens, appropriate light source and light collecting adaptor. The first objective of this study is to present the novel method for quantitative capillary shape analysis by using the level-set method. The capillary radius distribution along the capillary center line is obtained and described by the level-set function. Based on this mathematical description of capillary shape, more rigorous definition of the capillary red blood cell velocity than the conventional method is discussed. The second objective of this study is to propose the innovative measurement method of red blood cell velocity in nailfold capillary, and then the possibility of tracking the individual red blood cell movement, not only in the axial direction but also lateral direction, in human nailfold capillary is discussed - Fluid Dynamic Study on Budd-Chiari Syndrome: Sensitivity Study of Vessel Reconstruction on Image-Based Simulation
MATSUBARA Mizuho, WATANABE Masao, WATANABE Satoshi, KONISHI Kozo, YAMAGUCHI Shohei, HASHIZUME Makoto
JBSE, 2, 2, 69, 80, The Japan Society of Mechanical Engineers, 2007
English, Budd-Chiari syndrome (BCS) is a symptomatic complete or partial occlusion of the hepatic vein and/or the inferior vena cava. The cause of BCS is not well known yet, however; abnormal vessel wall shear stress caused by blood flow is thought to increase the likelihood of developing BCS. We investigate the blood flow field in the vicinity of the junction of the inferior vena cava and hepatic veins by using numerical simulation based on medical imaging. However, there exist inaccuracies in computational vessel models. The sensitivities of flow characteristics to vessel shape have not been fully investigated. In this study, the characteristics of the blood flow in the vicinity of the junction of the hepatic vein and the inferior vena cava are discussed based on the numerical results obtained by several reconstructed vessel models which are slightly different in shapes and surface smoothness. It is also demonstrated that relatively small differences in the shapes and surface smoothness of the reconstructed vessel model cause noticeable effects on the flow characteristics in the vicinity of the junction of the inferior vena cava and large hepatic veins. - 1444 High Speed Video Capillaroscopy and Capillary Vessel Blood Flow
IRIBE Masaki, KURODA Hiroaki, WATANABE Masao, MATSUBARA Mizuho, SANADA Toshiyuki
The proceedings of the JSME annual meeting, 2007, 87, 88, The Japan Society of Mechanical Engineers, 2007
Japanese, Nailfold video capillaroscopy (NVC) examines the micro vascular structure noninvasively and aids in the diagnosis of capillary disease, such as Raynaud's phenomenon. We developed high speed digital video capillaroscopy which is composed of high speed digital video camera, deep-focus lens, metal halide light source, and light collecting adaptor. We obtained sequential images of nailfold microcirculation loop with much higher temporal resolution than conventional capillaroscopy. The high speed digital video capillaroscopy enabled us to evaluate quantitatively both micro vascular structure and red blood cell movement. The objects of this study are to measure the radius distribution of micro vascular by Level Set method and also the red blood cell velocity by tracing plasma gap between blood cells. - 1468 Visualization of Single Rising Bubble Wake
TAKEDOMI Yuta, SATO Ayaka, SHIROTA Minori, SANADA Toshiyuki, WATANABE Masao
The proceedings of the JSME annual meeting, 2007, 133, 134, The Japan Society of Mechanical Engineers, 2007
Japanese, The structure of the flow around a rising bubble in silicone oil was visualized by using photochromic dye. We present the first experimental evidence of the existence of the standing eddy, which was predicted numerically by Blanco & Magnaudet[Phys. Fluids, Vol.7, 1265-1274(1995)]. We also experimentally evaluated two kinds of critical aspect ratios over which the standing eddy or three dimensional wake exists. It was found that experimentally obtained critical aspect ratios were smaller than those obtained numerically, however both experimental and numerical results qualitatively agree that critical aspect ratios were bigger in lower Reynolds number. - 1127 Image-based CFD of Blood Flow in the Hepatic Portion of the Inferior Vena Cava on Budd-Chiari Syndrome
MATSUBARA Mizuho, WATABANE Masao, WATANABE Satoshi, KONISHI Kozo, YAMAGUCHI Shohei, HASHIZUME Makoto
The proceedings of the JSME annual meeting, 2007, 93, 94, The Japan Society of Mechanical Engineers, 2007
Japanese, Budd-Chiari syndrome (BCS) is one of the vessel disorders caused by thrombosis which occlude partially or completely hepatic veins (HVs) and the inferior vena cava (IVC). It has been demanded to model the blood flow fields in the IVC and HVs to study the cause of formation of thrombosis. In order to analyze the blood flow fields, we carried out medical vessel segmentation of HVs and IVC using level set method, constructed 3D vessel model, and conducted computational fluid dynamics simulation by using velocity profile of the analytical solution for pulsatile flow in the IVC. - Bubble Wake Visualization by using Photochromic Dye
SANADA Toshiyuki, SHIROTA Minori, ONO Tomoki, WATANABE Masao
Transactions of the Visualization Society of Japan, 27, 7, 47, 52, The Visualization Society of Japan, Jan. 2007, [Peer-reviewed]
Japanese, Wake structure of zigzagging or spiraling motion of free rising bubbles was experimentally investigated. Single bubbles were generated in a silicone oil pool and the wake structure was visualized by using Phtochromic dye. Both bubble motion and wake were observed by using stereo high-speed video cameras. As results, a pair of vortex filaments, which is referred to as double-threaded type wake, was observed in the wake of a bubble rising in axi-asymmetric path. Periodical generation of horse-shoe type vortices were observed when the bubble rose with shape oscillations. - In-line motion of a pair of bubbles in a viscous liquid
M Watanabe, T Sanada
JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, 49, 2, 410, 418, JAPAN SOC MECHANICAL ENGINEERS, May 2006, [Peer-reviewed]
English, Scientific journal, We study the motion of a pair of bubbles rising in the vertical line, at intermediate Reynolds number (5 < Re < 150), both numerically and experimentally. It has been predicted, by analytical and numerical studies, that there exists a stable equilibrium distance between a pair of bubbles due to the balance between the potential repulsive and viscous atractive forces. However, no experimental results have ever confirmed the existence of an equilibrium distance between bubbles rising in a vertical line. Most experimental results indicated that a pair of bubbles collided. We solve this paradox and answer the question: "Is there an equilibrium distance?" by presenting both experimental evidence of an existence of the equilibrium distance and the detailed numerical results of a deforming-spatial-domain/space-time finite element method, taking bubble surface deformation effects into account. - 2533 Site calibration by with the aid of CFD
FUJINO Masatoshi, SHIROTA Minori, SANADA Toshiyuki, MATSUSHITA Daisuke, WATANABE Masao, MATSUMIYA Hikaru
The proceedings of the JSME annual meeting, 2006, 271, 272, The Japan Society of Mechanical Engineers, 2006
Japanese, In order to measure a wind turbine performance on a complex terrain that fails to satisfy the IEC standard, we should evaluate a flow correction factor which is the ratio of wind speeds between two points. In this study, we have compared the flow correction factors for 16 principal azimuthal directions between actual measurements and CFD results. From March in 2005 to February in 2006, wind speed and wind direction were measured by using two meteorological. And we calculate unsteady wind fields using highly accurate CFD method combined with both large eddy simulation and geographical information system. As a result, in 6 of 16 directions, the flow correction factors obtained from measurements differ from that obtained using CFD by only 〜10%. - 2606 Formation of single bubbles controlled with fluctuating gas pressure
SANADA Toshiyuki, SHIROTA Minori, ARATA Yasuhiro, WATANABE Masao
The proceedings of the JSME annual meeting, 2006, 273, 274, The Japan Society of Mechanical Engineers, 2006
Japanese, A method of a bubble production, originally developed by Kariyasaki and Osaka [Trans. JSME, 68-674B (2002)], is further investigated experimentally. First, the acoustic characteristic of the pipe between audio speaker and nozzle is investigated. Then, a new type of fluctuation consisted of both increase and decrease in gas pressure is used to clarify the effect of the fluctuation. Shrinking motion of a capillary bridge connecting a bubble and a nozzle was observed in detail using high-speed photography. We also estimate the force balance on a bubble center based on a spherical bubble formation model. As results, it is clarified that the pipe between speaker and nozzle could regard as acoustic tube. Moreover, when gas pressure is decreased the capillary bridge is sucked down into a nozzle and upward added mass force is applied on a bubble center, both of which cause the detachment of a bubble from a nozzle. - 4223 Bouncing and Coalescence of a pair of Bubbles in a Quiescent Liquid
SUGIHARA Keiji, ONO Tomoki, SHIROTA Minori, SANADA Toshiyuki, WATANABE Masao
The proceedings of the JSME annual meeting, 2006, 445, 446, The Japan Society of Mechanical Engineers, 2006
Japanese, We experimentally studied both bouncing and coalescence of a pair of bubbles rising side by side in a quiescent liquid. At high Reynolds number, a pair of bubbles approached each other and then collided. After the collision, bubbles either coalesced or bounced. We visualized flow field formed in the vicinity of bubbles by irradiating photochromic dye with UV light sheet, and observed wake of bubbles both before and after the collision. We discuss wake development of bubbles as bubbles collided and the relation between wake structure and bubble motion after the collision. We also investigated the critical Reynolds number and Weber number of coalescence of bubbles. We clarified that the critical Weber number is approximately two regardless of Morton number and that the critical Reynolds number decreases with the increase in Morton number. - 706 Macro-scale transport phenomena in articular cartilage
SUGINO Shouichi, KITAJIMA Yousuke, WATANABE Masao, SAWAE Yoshinori, SANADA Toshiyuki, MURAKAMI Teruo
The proceedings of the JSME annual meeting, 2006, 215, 216, The Japan Society of Mechanical Engineers, 2006
Japanese, Articular cartilage is charactericstic tissue which is mainly composed of avascular extracellular matrix. Solute transport in articular cartilage is to mainly by diffusion across the articular surface. We engineered regenerated cartilage by seeding bovine chondrocyte into agarose gel as scaffold. We evaluate diffusion coefficient by using fluorescent molecular with image process and to examine the effect of molecular weight and electric property of fluorescent labeled dextran on diffusion process in regenerated cartilage tissue. - 527 Image-based Computational Fluid Dynamics Study on Budd-Chiari Syndrome
MATSUBARA Mizuho, WATABANE Masao, WATANABE Satoshi, KONISHI Kozo, YAMAGUCHI Shohei, HASHIZUME Makoto
The proceedings of the JSME annual meeting, 2006, 109, 110, The Japan Society of Mechanical Engineers, 2006
Japanese, Budd-Chiari syndrome (BCS) is one of vessel disorders caused by thrombosis which occlude partially or completely hepatic vein and inferior vena cava. The cause of BCS has not been revealed yet, but it has been indicated that there are some relationships between BCS and blood flow fields in the vicinity of the confluence of hepatic vein with inferior vena cava. In order to analyze the blood flow fields, we carried out medical vessel segmentation of hepatic vein and vena cava using level set method with high accuracy, constructed 3D vessel model, and conducted computational fluid dynamics (image-based CFD). - Interaction and coalescence of bubbles in stagnant liquid
T. Sanada, M. Watanabe, T. Fukano
Multiphase Science and Technology, 18, 2, 155, 174, 2006, [Peer-reviewed]
English, Scientific journal, Interaction effects on the bubble motion and consequently induced coalescence were experimentally studied. A high accuracy bubble production control device enabled us to experiment various spatial configurations of a pair of bubbles. Among them, we focused on the cases where either bubbles rose in vertical line and side by side in silicone oil pool. Bubble diameter and liquid kinematic viscosity were taken as the experimental parameters. The motion of bubbles was recorded by a high-speed video camera. We observed that the Reynolds number Re significantly affected the motion of a pair of bubbles rising in both vertical line and side by side. When a pair of bubbles rose in vertical line, the trailing bubble was attracted by the wake of the leading bubble, and then it collided with leading bubble, in the case of low Re. On the other hand, in the case of intermediate Re, a pair of bubbles kept a mutual equilibrium distance due to the balance between the leading bubble wake attractive force and potential repulsive force. As Re further increased, the trailing bubble deformed and then escaped from the vertical line. When a pair of bubbles rose side by side, they separated from each other as they rose in the case of low Re. On the contrary, in the case of large Re, they attracted each other and then collided if the initial bubble horizontal distance was smaller than a critical value. At the moment of the collision of a pair of bubbles, we did not observe the significant deceleration of the bubble rising velocity. It should be noted that they collided with each other with asymmetric shape deformation. In addition, we investigate the criteria of either bouncing or coalescence of bubbles. Our experimental results show that the approach velocity is important parameter on coalescence of a pair of bubbles. - High-speed videomicroscopic in vivo analysis of human capillary vessel loop
T. Sanada, M. Watanabe, Y. Sawae, M. Furue
PROCEEDINGS OF THE 5TH WORLD CONGRESS OF BIOMECHANICS, 451, +, MEDIMOND S R L, 2006, [Peer-reviewed]
English, International conference proceedings, We developed high-speed video capillaroscopy and observed the capillary loops of blood vessels in finger skin nail fold. Deep-focus high magnification zoom lens and high speed video camera allowed us to observe the motion of red blood cells, white blood cells and plasmas. It should be emphasized that this method is non-invasive and non-blood observing diagnosis. Quantitative analysis of blood flow allowed us to observe the motion of red blood cell in a capillary vessel with the diameter from 10 micron to 20 micron with recording rate from 500 to 1000 Hz. We also conducted shape analysis of the capillary vessel, by using level set method. By analyzing the obtained level set function, quantitative evaluation of capillary blood shape, such as characteristic diameter and curvature are carried out. - Effects of viscosity on coalescence of a bubble upon impact with a free surface
T Sanada, M Watanabe, T Fukano
CHEMICAL ENGINEERING SCIENCE, 60, 19, 5372, 5384, PERGAMON-ELSEVIER SCIENCE LTD, Oct. 2005, [Peer-reviewed]
English, Scientific journal, Effects of liquid viscosity on coalescence of a bubble upon impact with a free surface were studied both experimentally and numerically. Experiments were conducted in a pool filled with silicone oil by generating a nitrogen gas bubble and observing it with a high-speed video camera. Full Navier-Stokes equations were solved with two level set functions for a bubble and a free surface. As a result, the Weber number was the most important parameter determining the coalescence time in low viscosity liquids. in contrast, the coalescence time in a high viscosity liquid was much greater than that of a low viscosity liquid with the same Weber number. In addition, the thresholds between bubble coalescence and bouncing were affected by liquid viscosity. For the differences in coalescence time, foam was observed at the free surface in the case of high viscosity case only the difference of liquid viscosity in the non-polar liquid. By examining the pressure distribution of the liquid film between the bubble and the free surface and the downward liquid flow, we conclude that not only the liquid film but also the liquid flow field underneath the bubble was important for bubble coalescence or bouncing. (c) 2005 Elsevier Ltd. All rights reserved. - Noninvasive in vivo Human Capillary Vessel Blood Flow analysis.
WATANABE MASAO, SANADA TOSHIYUKI, SAWAE YOSHINORI, FURUE MASUTAKA
日本臨床バイオメカニクス学会誌, 26, 91, 96, 01 Oct. 2005
Japanese - ヒト皮膚毛細管動静脈ループの高速度観察と血流動態解析
WATANABE MASAO, SANADA TOSHIYUKI, SAWAE YOSHINORI, MASUDA SADAKAZU, FURUE MASUTAKA
西日本皮膚科, 67, 5, 546, 01 Oct. 2005
Japanese - Behavior of a single coherent gas bubble chain and surrounding liquid jet flow structure
T Sanada, M Watanabe, T Fukano, A Kariyasaki
CHEMICAL ENGINEERING SCIENCE, 60, 17, 4886, 4900, PERGAMON-ELSEVIER SCIENCE LTD, Sep. 2005, [Peer-reviewed]
English, Scientific journal, The motion of a single nitrogen gas bubble chain and the structure of water flow field surrounding the chain were experimentally studied. We developed a bubble generator that can control both the bubble diameter and the generation frequency independently. Experimental conditions of bubble Reynolds number and bubble distance divided by bubble diameter were from 300 to 650 and from 6.5 to 300, respectively. We discuss the interaction effects on the motion of each bubble rising in a chain, as compared to the effects of a single rising bubble. The bubble trajectories and the surrounding water flow fields in the state of bubbles rising in a chain were investigated using a high-speed digital video camera and an analog single-lens-reflex camera. We observed two important physical phenomena. First, bubbles passed through a nearly identical path in the case of low frequency of bubble production. On the contrary, at a height of approximately 50 turn from the nozzle, the bubbles in the case of high frequency deviated and scattered from this path due to bubble-bubble interaction. Second, with higher bubble production frequency, coherent bubble chain and the characteristic structure of the surrounding water flow called "liquid jet" were observed near the nozzle. The direction of liquid jet flow differed from the bubble trajectory. We theoretically investigated the relation of coherent bubble chain and liquid jet by applying the conservation of liquid momentum. (c) 2005 Elsevier Ltd. All rights reserved. - ヒト皮膚毛細管動静脈ループの高速度観察と血流動態解析
FURUE MASUTAKA, MASUDA TEIICHI, WATANABE MASAO, SANADA TOSHIYUKI, SAWAE YOSHINORI
福岡医学雑誌, 96, 6, 277, 277, 福岡医学会, 25 Jun. 2005
Japanese, 人の末梢血管は皮膚表層の表皮下真皮乳頭層の血管を最小血管とする血流網を形成している.乳頭層の細小血管は皮膚表面を拡大すると,そのループの頂点を観察できるわけであるが,指爪郭の爪上皮(あまかわの所)部では,その全容を観察することが可能である.たとえば皮膚筋炎では,毛細管の拡張や出血が認められるが,爪郭の毛細管ではその病態がはっきりと可視化されている.本研究では,皮膚毛細管動静脈ループを流れる血流の血行動態を,毛細血管顕微鏡と高速度ビデオカメラとを組み合わせることにより,非侵襲・非観血で高時空間分解能に観察する手法を開発した. - Numerical site calibration in Takashima
FUJINO Masatoshi, SANADA Toshiyuki, MATSUSHITA Daisuke, UCHIDA Takanori, WATANABE Masao, MATUMIYA Hikaru
Proceedings of Japan Wind Energy Symposium, 27, 265, 268, Japan Wind Energy Association, 2005
Japanese - 210 In vivo flow and shape observation of human microcirculation
SANADA Toshiyuki, WATANABE Masao, SAWAE Yoshinori, FURUE Masutaka
Proceedings of the JSME Bioengineering Conference and Seminar, 2004, 57, 58, The Japan Society of Mechanical Engineers, 2005
Japanese - 232 Visualization of transport phenomena in engineered articular cartilage : Effect of chondrocyte metabolism
WATANABE Masao, SAWAE Yoshinori, SANADA Toshiyuki, HAARI Kenta, MURAKAMl Teruo
Proceedings of the JSME Bioengineering Conference and Seminar, 2004, 279, 280, The Japan Society of Mechanical Engineers, 2005
Japanese - Motion of a pair of bubbles rising in line
Masao Watanabe, Toshiyuki Sanada
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 71, 702, 389, 396, Japan Society of Mechanical Engineers, 2005
Japanese, Scientific journal, We study the motion of a pair of bubbles rising in the vertical line in intermediate Reynolds number, both numerically and experimentally. It has been predicted by the analytical and numerical studies that the trailing bubble approaches the leading bubble and then a pair of bubbles keeps the mutual equilibrium distance. However, no experimental results have ever confirmed the existence of the equilibrium distance between a pair of bubbles rising in the vertical line. Most of experimental results reported that a pair of bubbles collided. We solve this paradox and answer the question : "If there is an equilibrium distance?" by presenting the first experimental evidence of the existence of the equilibrium distance. Moreover we show that the equilibrium distance is considerably unstable by experimental results. - Quantitative Evaluation of Contour Segmentation of Three Dimensional Image Using Level Set Method
WATANABE MASAO, HIMENO RYUTARO
日本機械学会論文集 A編, 70, 697, 1276, 1283, The Japan Society of Mechanical Engineers, 25 Sep. 2004
Japanese, Quantitative evaluation of level set contour segmentation method applied to three dimensional images detecting image edge based on threshold is discussed. The integration of two popular level set methods, i.e., reinitialization method and geodesic active contour method, leads to success in development of robust, with high accuracy, level set based segmentation method. The applications of this method to both synthetic and clinical medical images are shown. Accuracy of the propose method, in the view of both averaged contour location and standard deviation of curvature in the vicinity of contour, calculated using obtained level set function is discussed. - Viscosity Effects on Coalescence of a Pair of Bubbles
Sanada Toshiyuki, Watanabe Masao, Sato Ayaka, Fukano Tohru
Asian Pacific Confederation of Chemical Engineering congress program and abstracts, 2004, 709, 709, The Society of Chemical Engineers, Japan, 2004
English, Effects of liquid viscosity on coalescence of a pair of bubbles were experimentally studied by generating nitrogen gas bubbles in a pool filled with silicon oil. We focused on two types of coalescence/bouncing of bubbles. The first type was those between a rising bubble and a free surface, and the second type was those between of a pair of bubbles rising side by side. The former is considered as the extreme case, which is equivalent to coalescence/bouncing between bubbles with finite and infinite diameters. The later is more practical. That is, bubbles were generated simultaneously from a pair of pin-holes on a pipe horizontally placed. We studied the viscosity effects on coalescence of bubbles by investigating behavior of bubbles with both liquid viscosity and bubble diameter as the parameters. Previous studies reported that We number based on approach velocity could predict whether two bubbles would bounce or coalesce in super purified water. Our experimental results show that the threshold We number in the case of low viscosity liquid indicates same order as the one in the case of super purified water. On the other hand, in the case of large viscosity liquid, the threshold We number differs significantly from the one in the super purified water. - Behavior of a pair of bubbles rising in line
WATANABE Masao, SANADA Toshiyuki
The proceedings of the JSME annual meeting, 2004, 355, 356, The Japan Society of Mechanical Engineers, 2004
Japanese, Behavior and shapes of a pair of bubbles rising in a viscous liquid were numerically analyzed by using DSD/ST (Deforming-Spatial-Domain/Space-Time) Finite Element Method in the cylindrical coordinate system. It has been predicted by the analytical and numerical studies that the trailing bubble approaches the leading bubble and then a pair of bubbles rising in the vertical line keeps the mutual equilibrium distance. However, no experimental results have ever confirmed the existence of the equilibrium distance between a pair of bubbles. In this study, we investigated the effects of bubble deformation on behavior of a pair of bubbles rising in line. We clarified that a pair of deformable bubbles reaches an equilibrium distance and the equilibrium distance is considerably unstable. - Viscosity Effects on Bouncing and Coalescence of a Pair of Bubbles
SANADA Toshiyuki, SATO Ayaka, WATANABE Masao, FUKANO Tohru
The proceedings of the JSME annual meeting, 2004, 351, 352, The Japan Society of Mechanical Engineers, 2004
Japanese, Effects of liquid viscosity on the coalescence of a pair of bubbles were experimentally studied by generating nitrogen gas bubbles in a pool filled with silicon oil. We focused on two types of coalescence/bouncing of bubbles, i.e., those between a rising bubble and a free surface, and between a pair of bubbles rising side by side. The former is considered as the extreme case, which is equivalent to coalescence/bouncing between bubbles with finite and infinite diameters. The later is more practical. That is, bubbles were generated simultaneously from a pair of pin-holes on a pipe horizontally placed. We studied the viscosity effects on coalescence of bubbles by investigating the behavior of bubbles with both liquid viscosity and bubble diameter as the parameters. Previous studies reported that We number based on approach velocity could predict whether two bubbles would bounce or coalesce in superpurified water. Our experimental results show that the threshold in the case of low viscosity liquid indicates the same order as the one in the case of superpurified water. On the other hand, in the case of a large viscosity liquid, the threshold differs significantly from the one in the superpurified water. - Dynamic simulation of the acoustic characteristics of bubble clouds (2nd report, on validity of continuum mathematical model)
Masao Watanabe, Andrea Prosperetti
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70, 691, 636, 643, Japan Society of Mechanical Engineers, 2004
Japanese, Scientific journal, The purpose of this study is to explore the validity of the continuum model by treating the bubbles individually accounting for their interaction exactly by numerical means. Using the equation set describing the bubble behavior including interactions in the bubble cloud, we simulate the acoustical characteristics of the bubble cloud. We compare eigenfrequencies and eigenvectors obtained from these equations with the continuum model results. We discuss the limits of the validity of the continuum model in detail, and answer the question
"How many bubbles can generate a bubble cloud from the acoustical point of view ?". - Bouncing and coalescence of a bubble approaching to free surface
Toshiyuki Sanada, Masao Watanabe, Tomohiro Yuda, Tohru Fukano
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70, 692, 863, 870, Japan Society of Mechanical Engineers, 2004
Japanese, Scientific journal, Bouncing and coalescence between single rising bubble and free surface were experimentally and numerically studied. In experimental study, with Weber number of O (10-2) ∼1.7 and Morton number of O(10 -9)O(10-4), it was observed that both liquid viscosity and bubble diameter are playing the dominant role in coalescence time and bounce/coalescence condition. It was clarified that Weber number is the important parameter in the coalescence, time of bubble with free surface in low viscosity liquid. However, in high viscosity liquid, scale of coalescence time was observed significantly different from the one of low viscosity liquid. In numerical study, the full Navier-Stokes equation was solved, by defining two Level Set functions for bubble and free surface respectively. The pressure of liquid film between bubble and free surface, bouncing mechanism and difference of coalescence time scales are discussed. - Viscosity effects on coalescence condition of a pair of bubbles
Toshiyuki Sanada, Masao Watanabe, Ayaka Sato, Tohru Fukano
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70, 700, 3128, 3135, Japan Society of Mechanical Engineers, 2004
Japanese, Scientific journal, Effects of liquid viscosity on the coalescence of a pair of bubbles were experimentally studied by generating nitrogen gas bubbles in a pool filled with silicone oil. We focused on two types of coalescence/bouncing of bubbles, i.e., those between a rising bubble and a free surface, and between a pair of bubbles rising side by side. The former is considered as the extreme case, which is equivalent to coalescence/bouncing between bubbles with finite and infinite diameters. The later is more practical. That is, bubbles were generated simultaneously from a pair of pin-holes on a pipe horizontally placed. We studied the viscosity effects on coalescence of bubbles by investigating the behavior of bubbles with both liquid viscosity and bubble diameter as the parameters. Previous studies reported that We number based on approach velocity could predict whether two bubbles would bounce or coalesce in superpurified water. Our experimental results show that the threshold in the case of low viscosity liquid indicates the same order as the one in the case of superpurified water. On the other hand, in the case of a large viscosity liquid, the threshold differs significantly from the one in the superpurified water. - Study on single bubble chains in stagnant water
Toshiyuki Sanada, Tohru Fukano, Masao Watanabe
Proceedings of the ASME/JSME Joint Fluids Engineering Conference, 2, 1489, 1496, American Society of Mechanical Engineers, 2003
English, International conference proceedings, The behaviors of single nitrogen gas bubble chains, with diameters of from 0.5 mm to 2.5 mm, in stagnant water were experimentally studied. We developed an innovative acoustic bubble generator, which can precisely control both bubble diameter and generation frequency in an independent manner. We discuss the effects of interactions between bubbles in bubble chains on the behaviors of each bubble quantitatively, comparing to those of single rising bubble. Bubble trajectories and surrounding water flow field generated by the bubble chains were carefully investigated by applying the image processing technique to the high-speed video camera data. We analyzed the experimental data and identified the following two significant physical phenomena. (1) Under the condition of bubble radii kept unchanged, while bubbles passed almost the same path in the current measurement region in the case of low generation frequency, they deviated from this path and scattered about 30 mm from the generator with the increase of bubble generation frequency. (2) With higher bubble generation frequency, characteristic structures of the surrounding flow fields were clearly observed. These flow fields possessed the planer structure which could be spanned by the bubble trajectory direction and vertical axis through bubble generator. - Effects of generation frequency and bubble diameter on the behaviors of single bubble chains
Toshiyuki Sanada, Masao Watanabe, Akira Kariyasaki, Tohru Fukano
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 69, 678, 307, 314, Japan Society of Mechanical Engineers, 2003
Japanese, Scientific journal, The effects of both generation frequency and bubble diameter on the behaviors of single bubble chains in stagnant water were experimentally investigated. We developed the bubble generator equipment to control precisely both bubble generation frequency and bubble diameter, independently. Bubbles were generated with diameters from 1.0 mm to 2.5 mm, and generation frequencies from 1 Hz to 20 Hz. We investigated bubble chain patters developments in stagnant water, by taking both generation frequency and diameter as parameters. Two types of bubble chain patterns were investigated carefully. The first type was the bubbles rising in zig-zag or helical. In this case the behaviors of bubbles with l/d >
100 (l : mutual distance d : diameter) were observed to be identical to those of single bubbles, on the contrary, those of bubbles with l/d <
50 ∼ 100 were influenced by the interaction by the other bubbles. The second type was the bubbles rising in line. The behavior of bubbles with l/d >
200 were indistinguishable from those of single bubble. - Single bubble chain behavior and liquid flow structures in the vicinity of a nozzle (liquid jet developments by single bubble chains)
Toshiyuki Sanada, Masao Watanabe, Hitomi Noda, Tohru Fukano
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 69, 687, 2446, 2452, Japan Society of Mechanical Engineers, 2003
Japanese, Scientific journal, The behavior of single nitrogen gas bubble chains and the structures of flow field in the vicinity of a nozzle were experimentally studied. Both bubble diameters and bubble generation frequencies were precisely controlled independently to be 2.2 mm, and from 1 Hz to 10 Hz (corresponding bubble distance
300∼30 mm), respectively, by using innovative acoustic device. Careful investigations of flow field in the vicinity of a nozzle by using Particle Image Velocimetry enabled us to investigate the following two significant physical phenomena. First, The lift forces acting on bubbles in the bubble chains were observed to increase as bubble generation frequency increases, and were largely affected by the preceding bubbles. Second, developments of characteristic liquid jet were identified to play a dominant role in generation of lift forces on each bubble in single bubble chains, and were theoretically investigated by applying the conservation of liquid momentum. - Blood flow field simulation and vessel segmentation in level set frame work for MR angiography (vessel wall description and velocity boundary condition)
Masao Watanabe, Ron Kikinis, Carl-Fredrik Westin
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 69, 687, 2408, 2415, Japan Society of Mechanical Engineers, 2003
Japanese, Scientific journal, A novel approach to correct magnetic resonance phase contrast angiography (MR-PCA) based on the coupling computational fluid dynamics (CFD) to vessel segmentation in the level set methodology. MR-PCA data is supplied not only to partial differential equation based fast local level set vessel segmentation as the initial condition, but also to CFD code using level set ghost fluid method as the initial and boundary conditions. These procedures are integrated to provide with the corrected velocity field in the most optimal vessel geometry. The application of this system to both synthetic and clinical data are shown and validity is discussed. - Dynamic Simulation of the Acoustic Characteristics of Bubble Clouds (1st Report, Construction of Mathematical Model)
Masao Watanabe, Andrea Prosperetti
Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 69, 688, 2612, 2619, Japan Society of Mechanical Engineers, 2003
Japanese, Scientific journal, A mathematical model discribing the acoustical characteristics of a bubble cloud containing N bubbles is derived taking bubble interaction effects into account. The method of multipole expansion, by using both singular perturbation method and the matching procedure, is carried out to determine the coefficients of the spherical harmonics expansion to satisfy boundary conditions of both on the bubble surfaces and at the infinity. Discrete characteristic equations are obtained from a set of N algebraic equations, under the assumption of potential flow and spherical bubble shape of bubbles. - Numerical Simulation of Bubble Motion by Using Finite Element Method with Time Dependent Non-Structured Mesh
Masao Watanabe, Rajendra Shrestha, Tohru Fukano
Proceedings of ASME/JSME Fluids Engineering Division Summer Meeting San Francisco, CA, USA. FEDSM99-7101, 99, 7101, 1999, [Lead author] - Numerical Analysis of Bubble Motion Using Finite Element Method with Time Dependent Non-Structured Interface Capturing Mesh
Masao Watanabe, Rajendra Shrestha, Tohru Fukano
Proceedings of 4th International Joint Symposium between Kyushu University and Chungnam National University, 96, 1999, [Lead author] - Experimental Study of the Behavior of Bubbles Rising in Stagnant Water
Masao Watanabe, Rajendra Shrestha, Tohru Fukano
Memoirs of the Graduate School of Engineering, Kyushu University, 59, 4, 243, 261, Kyushu University, 1999, [Lead author]
English - Bubble Cloud Collapse in an Inviscid and Incompressible Liquid
Masao Watanabe, Tohru Fukano
Proceedings of ASME/JSME Fluids Engineering Division Summer Meeting CA, USA. F. EDSM99-6771, 1999, [Lead author] - Numerical analysis of waves (viscous waves) generated on thin liquid film acompanied by gas flow
Takanari Inatomi, Tohru Fukano, Masao Watanabe
Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 65, 638, 3252, 3259, Japan Society of Mechanical Engineers, 1999
Japanese, Scientific journal, Viscous waves are generated on the gas-liquid interface of thin liquid film flowing concurrently with high speed gas flow in a horizontal rectangular duct when the flow rates of both gas and liquid are relatively small. It is well known that waves on the thin liquid film, such as viscous waves, play important roles on the breakdown and formation of liquid film. In the present paper we numerically investigate the nonlinear behavior and the flow conditions of generation of the viscous waves by solving two-dimensional incompressible Navier-Stokes equations of both phases with the Level Set method to capture the gas-liquid interface. - Hydrodynamic force between slightly deformable bubbles at low Reynolds number
M Watanabe, T Fukano
JSME INTERNATIONAL JOURNAL SERIES B-FLUIDS AND THERMAL ENGINEERING, 41, 2, 480, 485, JAPAN SOC MECHANICAL ENGINEERS, May 1998
English, Scientific journal, A new method is developed to solve the three-dimensional hydrodynamic field generated by multiple bubbles, which are arbitrarily configured at low Reynolds number, taking the effects of both bubble interactions and the slight deformation of the bubble surface into consideration, for the case of epsilon=We/Re<<1. The numerical results for the case of two equi-radial bubbles confirm the validity of this method with the restriction that the gap between the two bubbles is to be not less than half of the radius. It is shown that the hydrodynamic force acting as drag is smaller in the case of a bubble moving away from another stationary bubble than in the case of one bubble approaching another. This difference is explained as the nonlinear effect originating from the bubble surface deformation. - Complex Motions of Bubbles in Periodically Driven Pressure Field
Masao Watanabe, Tohru Fukano
Proceedings of International Conference of Multiphase Flow '98, Lyon, France, 1998, [Lead author] - A simplified model for linear and nonlinear processes in thermoacoustic prime movers .1. Model and linear theory
M Watanabe, A Prosperetti, H Yuan
JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, 102, 6, 3484, 3496, AMER INST PHYSICS, Dec. 1997
English, Scientific journal, A simplified quasi-one-dimensional model of thermoacoustic devices is formulated by averaging the conservation equations over the cross section. Heat transfer and drag effects are introduced by means of suitable coefficients. While the primary motivation for this work is the development of a model approximately valid in the nonlinear regime, the focus of this paper is the proper formulation of the transfer coefficients and the analysis of the linear problem. The accuracy of the model is demonstrated by comparison with existing more precise theories and data. Examples of devices with variable cross section demonstrate the flexibility of the approach. (C) 1997 Acoustical Society of America. [S0001-4966(97)01412-4]. - Liquid film formation on the inner surface of the horizontal channel
T Fukano, H Nakagawa, Y Mori, M Watanabe
NUCLEAR ENGINEERING AND DESIGN, 175, 1-2, 3, 13, ELSEVIER SCIENCE SA, Nov. 1997, [Peer-reviewed]
English, Scientific journal, In a horizontal channel a separated how usually occurs if the size of the channel is not as small as a capillary tube and the flow rates of both phases of gas and liquid are low. If the how rate of gas exceeds a certain value, liquid begins to climb up the inner surface of the channel. The higher the gas velocity, the higher the film climbs up toward the top of the channel cross section. The present paper is concerned with the experimental investigation of the role of large scale waves, or disturbance waves, in the formation of liquid film on the side wall of a horizontal channel. The thinning process of liquid film thickness as the function of time is also investigated by a simple liquid flow model. (C) 1997 Elsevier Science S.A. - SHOCK-WAVES IN DILUTE BUBBLY LIQUIDS
M WATANABE, A PROSPERETTI
JOURNAL OF FLUID MECHANICS, 274, 349, 381, CAMBRIDGE UNIV PRESS, Sep. 1994
English, Scientific journal, The propagation of weak shock waves in liquids containing a small concentration of gas bubbles is studied theoretically on the basis of a mathematical model that contains all - and only - the effects that contribute to first order in the gas volume fraction. In particular, the thermal exchange between the gas bubbles and the liquid is described accurately. This aspect of the theory emerges:as its most significant component, relegating effects such as the relative motion between the phases to roles of minor importance. Comparison with experimental results substantiates the accuracy of the model for shock waves that have had time to broaden from an initial sharp front to a more diffuse profile. For shock waves closer to inception, marked differences are found between theory and experiment. The same problem affects all other published theoretical treatments. It is concluded that some as yet poorly understood mechanism governs the early-time behaviour of shock waves in bubbly liquids. - The Effect of Gas Diffusion on the Nuclei Population Downstream of a Cavitation Zone
Masao Watanabe, Andrea Prosperetti
Proceedings of the Symposium on Cavitation and Gas-Liquid Flow in Fluid Machinery and Devices, FED-Vol. 190, 211, 1994, [Lead author] - Mass Diffusion Effects on Cavitation Nuclei
Masao Watanabe, Andrea Prosperetti
Proceedings of 2nd International Symposium and Cavitation, Tokyo Japan, 321, 1994, [Lead author] - Numerical simulation on a bubble motion with full N-S equations.
Yoichiro MATSUMOTO, Masao WATANABE
TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B, 55, 519, 3282, 3287, Japan Society of Mechanical Engineers, 1989
Scientific journal - Numerical simulation on a bubble motion with full N-S equations.
Yoichiro MATSUMOTO, Masao WATANABE
TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B, 55, 519, 3282, 3287, Japan Society of Mechanical Engineers, 1989
Scientific journal - Nonlinear Oscillation of Gas Bubble with Internal Phenomena
Yoichiro Matsumoto, Masao Watanabe
JSME International Journal, Series II, 32, 2, 157, 1988 - Nonlinear Oscillation of Gas Bubble Considering the Internal Phenomena
Yoichiro MATSUMOTO, Masao WATANABE
TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B, 54, 501, 1051, 1057, The Japan Society of Mechanical Engineers, 1988
Japanese, The pressure response of a small air bubble in water is calculated numerically in an oscillatory pressure field. The following phenomena are taken into account in the calculation ; mist formation inside the bubble due to homogeneous condensation, diffusion between vapor and noncondensable gas inside the bubble and so on. The internal condition adapts itself easily to the oscillatory pressure field by the internal phenomena, which includes mist formation, evaporation and deposition onto the bubbler wall, so that the bubble tends to oscillate synchronously. The frequency response curves for bubbles are calculated. The curve is shifted towards low frequency, and the maximum bubble radius becomes large. When the pressure amplitude is increased, the periodic bubble oscillation bifurcates to non-periodic oscillation, which is a deterministic chaos. - Nonlinear oscillation of gas bubble with internal phenomena.
MATSUMOTO Yoichiro, WATANABE Masao
Transactions of the Japan Society of Mechanical Engineers Series C, 54, 501, 1051, 1057, The Japan Society of Mechanical Engineers, 1988
Japanese, The pressure response of a small air bubble in water is calculated numerically in an oscillatory pressure field. The following phenomena are taken into account in the calculation ; mist formation inside the bubble due to homogeneous condensation, diffusion between vapor and noncondensable gas inside the bubble and so on. The internal condition adapts itself easily to the oscillatory pressure field by the internal phenomena, which includes mist formation, evaporation and deposition onto the bubbler wall, so that the bubble tends to oscillate synchronously. The frequency response curves for bubbles are calculated. The curve is shifted towards low frequency, and the maximum bubble radius becomes large. When the pressure amplitude is increased, the periodic bubble oscillation bifurcates to non-periodic oscillation, which is a deterministic chaos.
Other Activities and Achievements
- エタノール液滴のスプラッシュ発生に及ぼす蒸気の凝縮効果
澤井 冴, 渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之, 流体工学部門講演会講演論文集, 2018, OS2-17, May 2019, [Peer-reviewed]
Japanese, Summary national conference - 単一液滴衝突時に取り込まれる空気膜の観察
Riichiro Endo, Masao Watanabe, Kazumichi Kobayashi, Hiroyuki Fujii, 流体工学部門講演会講演論文集, 2018, OS2-5, May 2019, [Peer-reviewed]
Japanese, Summary national conference - Numerical study of light scattering in the human neck for diagnosis of thyroid cancers by optical tomography
Fujii Hiroyuki, Yamada Yukio, Hoshi Yoko, Kobayashi Kazumichi, Watanabe Masao, Extended abstract of the 12th CME International Conference, OS12, 2, 2018
English, Summary international conference - 分子動力学法を用いた高温壁へ衝突するナノ液滴の浮遊メカニズム解析
田部 広風海, 小林 一道, 矢口 久雄, 藤井 宏之, 渡部 正夫, マイクロ・ナノ工学シンポジウム, 2018.9, 30pm4PN16, 2018, [Peer-reviewed]
Japanese, Summary national conference - 高温壁へ衝突する液滴の浮遊メカニズムに関する分子動力学解析
田部 広風海, 小林 一道, 矢口 久雄, 藤井 宏之, 渡部 正夫, 流体工学部門講演会講演論文集, 2018, OS2-1, 2018, [Peer-reviewed]
Japanese, Summary national conference - 粘弾性乳液滴と固体表面の高速衝突の観察
伊藤 一樹, 芦田 拓, 渡部 正夫, 小林 一道, 藤井 宏之, 吉岡 孝一郎, 大井 航, 髙野 真, 流体工学部門講演会講演論文集, 2018, OS2-23, 2018, [Peer-reviewed]
Japanese, Summary national conference - 低圧環境下における高速液滴衝突直後に発生するsplashの観察
芦田 拓, 渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之, 流体工学部門講演会講演論文集, 2018, OS2-9, 2018, [Peer-reviewed]
Japanese, Summary national conference - Numerical Calculation Of Time-resolved Light Reflectance From Biological Tissue Using The Radiative Transfer Equation
Hiroyuki Fujii, Yukio Yamada, Yoko Hoshi, Kazumichi Kobayashi, Masao Watanabe, Extended abstract of The International Conference on Mathematics in (bio)Chemical Kinetics and Engineering (MaCKiE) 2017, 2017
English, Summary international conference - 拡散光による甲状腺腫瘍診断のためのヒト頸部内における光伝播の数値解析
藤井 宏之, 山田 幸生, 星 詳子, 小林 一道, 渡部 正夫, 第33回近赤外フォーラム 講演論文集, I, 07, 2017
Japanese, Summary national conference - Laboratory of Fluid Dynamics, Division of Mechanical and Space Engineering, Faculty of Engineering, Hokkaido University
渡部 正夫, 小林 一道, 藤井 宏之, 混相流 = Japanese journal of multiphase flow, 30, 4, 408, 411, Dec. 2016
日本混相流学会, Japanese - 蒸気と気体で満たされた球形気泡の収縮・膨張運動に関する分子気体力学解析
永山 貴大, 今 美沙紀, 小林 一道, 渡部 正夫, 藤井 宏之, 高比良 裕之, 流体工学部門講演会講演論文集, 2016, 0727, 2016, [Peer-reviewed]
Japanese, Summary national conference - Best Presentation Award in JSMF Multiphase Flow Symposium 2015
渡部 正夫, 混相流 = Japanese journal of multiphase flow, 29, 4, 386, 389, Dec. 2015
日本混相流学会, Japanese - 流体物理洗浄(3)ジェット洗浄、ブラシ洗浄、その他
真田 俊之, 渡部正夫, ケミカルタイムズ, 238, (num), 22, 27, 01 Oct. 2015 - 流体物理洗浄(3)ジェット洗浄,ブラシ洗浄,その他
SANADA TOSHIYUKI, WATANABE MASAO, Chem Times, 2015, 4, 16, 21, 01 Oct. 2015
Japanese - J0540204 Numerical simulation of gas shear flow between liquid slab and solid wall by using Enskog-Vlasov equation
KON Misaki, KOBAYASHI Kazumichi, WATANABE Masao, Mechanical Engineering Congress, Japan, 2015, "J0540204, 1"-"J0540204-3", 13 Sep. 2015
The aim of this study is to investigate the relation between the slip velocity at the gas-liquid interface and the rarefaction. We carried out the numerical simulation of the steady shear flow between the liquid slab and the solid wall with changing Knudsen number based on mean field kinetic theory. The simulation results showed that the slip velocity at the gas-liquid interface increases with the increase of Knudsen number. On the other hand, the slip velocity at the gas-solid interface is smaller than that at the gas-liquid interface in all cases of Knudsen number., The Japan Society of Mechanical Engineers, Japanese - J0540301 Numerical Computation of a Mathematical Model Applying Boundary Conditions Derived from Molecular Gas Dynamics at Gas-Liquid Interface for Describing Bubble Behaviors Accompanied by Phase Changes
MORIKAWA Shotaro, JINBO Yoshinori, TATEKURA Yuki, KOBAYASHI Kazumichi, WATANABE Masao, Mechanical Engineering Congress, Japan, 2015, "J0540301, 1"-"J0540301-5", 13 Sep. 2015
The collapse and rebound of a single spherical bubble with phase changes at the vapor-iquid interface are fundamental physical phenomena in the fields of industry and medicine. In this study, we propose a mathematical model of describing the dynamics of a spherical vapor bubble with phase changes (evaporation and condensation) at the vapor-liquid interface. To deal with evaporation and condensation phenomena at the interface precisely, we utilize the boundary condition of the interface derived from the molecular gas dynamics analysis. The calculation results of the mathematical model show that the maximum pressure inside a bubble due to the bubble collapse with phase changes becomes higher than that of the bubble collapse without phase changes., The Japan Society of Mechanical Engineers, Japanese - 流体物理洗浄(1)基本概念と微粒子の付着力
SANADA TOSHIYUKI, WATANABE MASAO, Chem Times, 2015, 2, 17, 23, 01 Apr. 2015
Japanese - Numerical analysis of photon migration in three-dimensional turbid media using the delta-Eddington approximation
Hiroyuki Fujii, Shinpei Okawa, Ken Nadamoto, Eiji Okada, Yukio Yamada, Yoko Hoshi, Masao Watanabe, Extended abstract of the 9th CME International Conference, OS6, 4, 2015
English, Summary international conference - 反射衝撃波によって誘起される非凝縮性気体を伴う蒸気の凝縮現象に関する分子気体力学に基づく数値計算
永山 貴大, 藤井 宏之, 小林 一道, 渡部 正夫, 日本機械学会年次大会, 2015, J0540205, 2015
Japanese, Summary national conference - シリンジを用いた高速液滴射出装置の開発および液滴衝突の観察
片岡 豊, 堀 優作, 渡部 正夫, 小林 一道, 藤井 宏之, 日本機械学会年次大会, 2015, G0500203, 2015
Japanese, Summary national conference - 異なる境界条件を課した生体モデルにおける光伝播の数値解析
服部 聖仁, 藤井 宏之, 小林 一道, 渡部 正夫, 日本機械学会年次大会, 2015, J2410103, 2015
Japanese, Summary national conference - 固体壁面の濡れ性が液滴衝突により発生する流れの進展挙動に与える影響の観察
山口 陽平, 渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之, 流体工学部門講演会講演論文集, 2015, 317, 2015, [Peer-reviewed]
Japanese, Summary national conference - 低圧環境下での高速液滴衝突によるSplash発生の観察
東 稜, 渡部 正夫, 小林 一道, 藤井 宏之, 流体工学部門講演会講演論文集, 2015, 318, 2015, [Peer-reviewed]
Japanese, Summary national conference - シリンジを用いた高速微細液滴射出装置の開発
堀 優作, 片岡 豊, 渡部 正夫, 小林 一道, 藤井 宏之, 流体工学部門講演会講演論文集, 2015, 319, 2015, [Peer-reviewed]
Japanese, Summary national conference - エタノール液滴と固体壁の衝突現象に周囲気体種が及ぼす影響
磯野 俊悠, 渡部 正夫, 小林 一道, 藤井 宏之, 日本機械学会年次大会, 2015, G0500202, 2015
Japanese, Summary national conference - 生体光イメージングのためのヒト頸部内光伝播モデルの構築
藤井 宏之, 大川 晋平, 灘本 健, 岡田 英史, 山田 幸生, 星 詳子, 渡部 正夫, バイオエンジニアリング講演会講演論文集, 2015.27, 1G21, Jan. 2015
Japanese, Summary national conference - Student Presentation Award in JSMF Multiphase Flow Symposium 2013
渡部 正夫, 混相流, 27, 4, 472, 476, Dec. 2013
日本混相流学会, Japanese - J053025 Numerical Simulation for Kinetic Boundary Condition at a Vapor-Liquid Interface Based Enskog-Vlasov Equation
KOBAYASHI Kazumichi, KON Misaki, OHASHI Kotaro, WATANABE Masao, Mechanical Engineering Congress, Japan, 2013, "J053025, 1"-"J053025-4", 08 Sep. 2013
The aim of the present study is to investigate the kinetic boundary condition (KBC) at a vapor-liquid interface in net evaporation/condensation states by using the Enskog-Vlasov equation. Our target system is a steady evaporation and condensation state between two liquid slabs with different temperatures. The results show that we can realize the simulation of steady evaporation and condensation phenomena between the two-liquid slabs with different temperature. Also, the normal and tangential temperatures including the kinetic boundary condition is not only the function of molecular energy flux but also the function of molecular collision mass flux in net condensation interface., The Japan Society of Mechanical Engineers, Japanese - J053024 Molecular dynamics analysis on evaporation of argon liquid in argon-neon system
HORI Kazumasa, YAHAGI Takato, TAKEUCHI Shinnosuke, YAGUCHI Hisao, KOBAYASHI Kazumichi, WATANABE Masao, Mechanical Engineering Congress, Japan, 2013, "J053024, 1"-"J053024-5", 08 Sep. 2013
The aim of the present study is to establish the kinetic boundary condition of a vapor-liquid interface for argon-neon two-component systems by using the molecular dynamics simulation. Two kinds of simulations were conducted: vapor-liquid equilibrium and evaporation simulations at the liquid temperature 85 K. In this paper, we investigated the influence of mole rate of neon for the evaporation flux of argon and calculated the value of the evaporation coefficient. The results show that as the mole rate of neon increases, the evaporation coefficient of argon becomes smaller. The main factor for the decrease of evaporation coefficient is the increase of the outgoing molecular mass flux at the equilibrium states due to the increase of mole rate of neon. Further, the velocity distribution function of argon composed of the evaporating molecules deviates from the half - Maxwellian with the liquid temperature., The Japan Society of Mechanical Engineers, Japanese - Numerical analysis of nonequilibrium evaporation/condensation phenomena by Enskog-Vlasov equation
Kon Misaki, Kobayashi Kazumichi, Watanabe Masao, Meeting abstracts of the Physical Society of Japan, 68, 2, 248, 248, 26 Aug. 2013
The Physical Society of Japan (JPS), Japanese - 304 Numerical analysis of high-speed droplet spray flow in cleaning nozzle
Tamura Toshiyuki, Kawahara Junya, Kobayashi Kazumichi, Watanabe Masao, 北海道支部講演会講演概要集, 2012, 51, 83, 84, 20 Oct. 2012
The Japan Society of Mechanical Engineers, Japanese - (9)Unified Theory Based on Parameter Scaling for Derivation of Nonlinear Wave Equations in Bubbly Liquids
金川 哲也, 矢野 猛, 渡部 正夫, 藤川 重雄, Journal of the Japan Society of Mechanical Engineers, 115, 1122, 265, 266, 05 May 2012
The Japan Society of Mechanical Engineers, Japanese - J054032 Molecular Gas Dynamics on Resonant Gas Oscillations Accompanied with Phase Changes at Vapor-Liquid Interface
INABA Masashi, YANO Takeru, WATANABE Masao, KOBAYASHI Kazumichi, FUJIKAWA Shigeo, Mechanical Engineering Congress, Japan, 2011, "J054032, 1"-"J054032-2", 11 Sep. 2011
The resonant gas oscillation excited in a one-dimensional space between an oscillating plate and a planer surface of a thin liquid layer on a quiescent rigid-wall is considered. Vapor flows with evaporation or condensation at the vapor-liquid interface are theoretically studied on the basis of a polyatomic version of Gaussian-BGK Boltzmann equation with a kinetic boundary condition including an evaporation coefficient., The Japan Society of Mechanical Engineers, Japanese - J054031 Measurements of the Evaporation Coefficient of Water Using Sound Resonance Method
NAKAMURA Shigeto, YANO Takeru, KOBAYASHI Kazumichi, WATANABE Masao, FUJIKAWA Shigeo, Mechanical Engineering Congress, Japan, 2011, "J054031, 1"-"J054031-4", 11 Sep. 2011
We propose a new method for measurement of the evaporation coefficient using sound resonance experiment based on a theory of molecular gas dynamics. The evaporation coefficient is one of the parameters contained in the kinetic boundary condition. The evaporation coefficient of water is determined from the pressure amplitude of resonant sound wave in a cylindrical space bounded by a sound source and a vapor-liquid interface. By comparing the pressure amplitude with a linear theory based on molecular gas dynamics, we prove that the evaporation coefficient of water is about 1.0 around 300K., The Japan Society of Mechanical Engineers, Japanese - J054033 Numerical Simulations for Couette flows in Dense Gas Based on Enskog Equation
KOBAYASHI Kazumichi, OHASHI Kotarou, INABA Masashi, WATANABE Masao, FUJIKAWA Shigeo, Mechanical Engineering Congress, Japan, 2011, "J054033, 1"-"J054033-5", 11 Sep. 2011
Numerical simulations for Couette flows in a dense gas are conducted based on the Enskog equation. In order to solve the Enskog equation, we use the particle scheme method, which is an extension of the well known DSMC method that is used to solve the Boltzmann equation. The results agree well with the solution of the Boltzmann equation, as the ratio of molecular diameter to the mean free path of the molecules, a/ A, becomes smaller. A thin layer is formed near a solid wall surface as the ratio al A becomes larger. We also find that the slip velocity on the solid surface depends on the ratio al A., The Japan Society of Mechanical Engineers, Japanese - Report on the 14th Organized Multiphase Flow Forum (OMF2010-Jozankei)
MURAI Yuichi, NARABAYASHI Tadashi, WATANABE Masao, Japanese journal of multiphase flow, 25, 1, 60, 63, 15 Mar. 2011
日本混相流学会, Japanese - 403 Human Nailfold Capillary Shape Analysis and Red Blood Cell Velocity Measurement
佐野 宏典, 矢口 久雄, 小林 一道, 渡部 正夫, 藤川 重雄, 北海道支部講演会講演概要集, 2010, 49, 83, 84, 07 Nov. 2010
The Japan Society of Mechanical Engineers, Japanese - 0407 Nonlinear Waves in Liquid Containing Microbubbles Encapsulated by Visco-Elastic Shell
KANAGAWA Tetsuya, WATANABE Masao, YANO Takeru, FUJIKAWA Shigeo, Fluids engineering conference ..., 2010, 133, 134, 29 Oct. 2010
Nonlinear propagation of pressure waves in an initially quiescent liquid containing non-uniformly distributed spherical microbubbles is theoretically studied on the basis of the method of multiple scales. We focus on almost unidirectional waves propagating mainly in one direction with a weak diffraction or weak focusing to the transverse direction (like a ultrasound beam). Based on a methodology recently proposed by the authors, the KZK type equation, in which the dispersion and the non-uniformity of number density of bubbles are considered, is derived from the basic equations of bubbly flows., The Japan Society of Mechanical Engineers, Japanese - 301 Evaluation of Evaporation Coefficient at Spherical Vapor-Liquid Interface of Nanodroplet
矢口 久雄, 矢野 猛, 渡部 正夫, 藤川 重雄, The Computational Mechanics Conference, 2010, 23, 292, 294, 23 Sep. 2010
The Japan Society of Mechanical Engineers, Japanese - 303 マイクロ液滴噴霧洗浄技術開発のための高速ノズル流動解析(OS3. ナノ・マイクロ熱流動現象(1),オーガナイズドセッション講演)
高橋 広樹, 渡部 正夫, 小林 一道, 藤川 重雄, 計算力学講演会講演論文集, 2010, 23, 297, 298, 23 Sep. 2010
一般社団法人日本機械学会, Japanese - 302 壁面に衝突する高速マイクロ液滴挙動に及ぼす液滴温度の効果(OS3. ナノ・マイクロ熱流動現象(1),オーガナイズドセッション講演)
ユ ヨンゼ, 渡部 正夫, 小林 一道, 藤川 重雄, 計算力学講演会講演論文集, 2010, 23, 295, 296, 23 Sep. 2010
一般社団法人日本機械学会, Japanese - Weakly Nonlinear Analysis for Resonant Gas Oscillations with Evaporation and Condensation
Inaba Masashi, Yano Takeru, Watanabe Masao, Kobayashi Kazumichi, Fujikawa Shigeo, 日本流体力学会年会講演論文集, 2010, 102, 102, 2010
The behavior of resonant sound waves in a finite one-dimensional space between an oscillating plate (sound source) and a vapor-liquid interface is analyzed by applying the asymptotic theory for Kn<Evaporation Coefficient at a Spherical Vapor-Liquid Interface
Yaguchi Hisao, Yano Takeru, Watanabe Masao, Fujikawa Shigeo, 日本流体力学会年会講演論文集, 2010, 284, 284, 2010
Kinetics of phase change at spherical interface between an argon nanodroplet and its vapor is studied by molecular dynamics simulation. The evaporation coefficient is evaluated at spherical control surface around the nanodroplet at 85K, however it depends on not only a radius of the nanodroplet but also that of control surface. Thus we define a new specific control surface, where the mass flux of evaporating molecules from the nanodroplet into vacuum is equal to that from the planar liquid film. The specific surface is found to be in a few nanometers distance from the center of the vapor-liquid transition layer. We adopt this surface as a interface for evaluating evaporation coefficient and successfully determine the evaporation coefficients for argon nanodroplets ranging from 1 to 4nm in radius. As a result, the evaporation coefficient decreases with decreasing in the radius of the nanodroplet., 日本流体力学会, JapaneseWeakly Nonlinear Propagation of Sound Beam in Bubbly Liquids
KANAGAWA Tetsuya, WATANABE Masao, YANO Takeru, FUJIKAWA Shigeo, 日本流体力学会年会講演論文集, 2010, 258, 258, 2010
Weakly nonlinear propagation of pressure waves in an initially quiescent liquid containing many small spherical gas bubbles is studied for the case of low frequency and long wavelength. We focus on almost unidirectional waves propagating mainly in one direction with a weak diffraction to the transverse direction (like a ultrasound beam), i.e., weakly two-dimensional waves. On the basis of a methodology recently proposed by ourselves, the KZK equation with a dispersion term is systematically derived from the basic equations of bubbly flows., 日本流体力学会, JapaneseNovel Method for Measurement of Evaporation Coefficient
Nakamura Shigeto, Yano Takeru, Kobayashi Kazumichi, Watanabe Masao, Fujikawa Shigeo, 日本流体力学会年会講演論文集, 2010, 283, 283, 2010
We propose a new method for measurement of the evaporation coefficient using nonlinear sound resonance experiment based on a theory of molecular gas dynamics. The evaporation coefficient is determined from the pressure amplitude of second harmonics generated by the nonlinear effect of resonant sound wave in a cylindrical space bounded by a sound source and a gas-liquid interface. To demonstrate the applicability of this method, we conduct a test experiment. As a result, we confirm the increase of second harmonics amplitude caused by the sound resonance., 日本流体力学会, Japanese206 Development of Low-pressure Submerged Water Jet for Organic Compounds Decomposition
中村 謙介, 渡部 正夫, 藤川 重雄, 北海道支部講演会講演概要集, 2009, 48, 45, 46, 28 Nov. 2009
The Japan Society of Mechanical Engineers, Japanese1605 Visualization of Nailfold Micro-circulation Using High-speed Video Capillaroscopy
WATANABE Masao, NAKAMURA Yuuki, SANO Hironori, YAGUCHI Hisao, Fluids engineering conference ..., 2009, 491, 492, 06 Nov. 2009
Capillaroscopy is a "lens" that is able to observe capillary loops of blood vessels in the human finger skin nail fold, of which blood flow can be easily visualized, and has been long used for clinical diagnosis. We have been developing digital high speed video capillaroscopy by integrating to high-speed high-sensitivity video camera with deep-focus zoom lens. We discuss quantitative evaluation of blood velocity in both arteriol and venule of human nailfold microcirculation, using two different methods, namely, plasma gap tracking method and fixed point observation method with correlation., The Japan Society of Mechanical Engineers, Japanese30aTJ-5 Molecular Dynamics Study of Vapor-liquid Equilibrium Condition of Nanodroplet
Yaguchi Hisao, Yano Takeru, Watanabe Masao, Fujikawa Shigeo, Meeting abstracts of the Physical Society of Japan, 64, 1, 319, 319, 03 Mar. 2009
The Physical Society of Japan (JPS), Japanese318 Noninvasive Observation of Red Blood Cell Dynamics with High Speed Digital Video Capillaroscopy
NAKAMURA Yuuki, IRIBE Masaki, MATSUBARA Mizuho, WATANABE Masao, バイオエンジニアリング講演会講演論文集, 2008, 21, 127, 128, 22 Jan. 2009
The Japan Society of Mechanical Engineers, Japanese508 Transport Phenomena in Scaffold Gel for Engineered Cartilage
NOBAYASHI Makoto, WATANABE Shouhei, NODA Hiroyuki, SAWAE Yoshinori, WATANABE Masao, バイオエンジニアリング講演会講演論文集, 2008, 21, 199, 200, 22 Jan. 2009
The Japan Society of Mechanical Engineers, JapaneseMolecular Gas Dynamics on Resonant Sound Waves Excited in One-Dimensional Space between Oscillating Plate and Vapor-Liquid Interface
INABA Masashi, YANO Takeru, WATANABE Masao, FUJIKAWA Shigeo, 日本流体力学会年会講演論文集, 2009, 124, 124, 2009
The behavior of resonant sound waves in a finite one-dimensional space between an oscillating plate (sound source) and a vapor-liquid interface is analyzed by applying the asymptotic theory for Kn<Evaluation of Evaporation Coefficient at the Vapor-liquid Interface of Argon Nanodroplet by Molecular Dynamics Method
Yaguchi Hisao, Yano Takeru, Watanabe Masao, Fujikawa Shigeo, 日本流体力学会年会講演論文集, 2009, 217, 217, 2009
Mass fluxes and evaporation coefficients at the interface between an argon nanodroplet and its vapor are investigated by nonequilibrium molecular dynamics (MD) simulations. The simulations are carried out at the temperatures of 85, 90, 95, 100, and 105K with droplet radii ranging from about 1nm to 4nm. The evaporation mass fluxes J_are obtained by MD simulations of evaporation into vacuum and are found to be almost independent of droplet radius at the specified control surface R_ . Since the outgoing mass flux J_ in an equilibrium state becomes large as the droplet radius does small, the evaporation coefficient α_e, defined by the ratio of J_ to J_ , decreases with decrease in the droplet radius., 日本流体力学会, Japanese Weakly Nonlinear Propagation of Quasi-Monochromatic Waves in Bubbly Liquids
Kanagawa Tetsuya, Yano Takeru, Watanabe Masao, Fujikawa Shigeo, 日本流体力学会年会講演論文集, 2009, 175, 175, 2009
One-dimensional nonlinear dispersive waves in a liquid containing a number of small spherical gas bubbles are theoretically studied based on a set of two-fluid averaged equations composed of the conservation laws of mass and momentum for gas and liquid phases, and the Keller equation for the bubble dynamics. The liquid compressibility is taken into account, and this leads to the wave attenuation due to bubble oscillations. By using an appropriate scaling of physical parameters and the method of multiple scales, we can derive the nonlinear Schrodinger equation with an attenuation term due to the acoustic radiation and the liquid viscosity. This equation describes a far field of a quasi-monochromatic wave train in the bubbly liquid, which evolves into a slowly modulated wave packet as a result of long range propagation of weakly nonlinear waves with the strong dispersion effect., 日本流体力学会, Japanese門脈血行異常症に関する調査研究 バッドキアリ症候群機序解明のためのイメージベースドCFDによる流体力学的解析
HASHIZUME MAKOTO, WATANABE MASAO, MATSUBARA MIZUHO, KONISHI KOZO, 門脈血行異常症調査研究班 平成20年度研究報告書, 26, 29, 2009
Japanese門脈血行異常症に関する調査研究 バッドキアリ症候群機序解明のためのイメージベースドCFDによる流体力学的解析
HASHIZUME MAKOTO, WATANABE MASAO, MATSUBARA MIZUHO, KONISHI KOZO, 門脈血行異常症調査研究班 平成20年度研究報告書, 87, 89, 2009
Japanese7・2 流体計測(7.流体工学,<特集>機械工学年鑑)
速水 洋, 青木 俊之, 半田 太郎, 田中 和博, 林 秀千人, 佐田富 道雄, 古川 明徳, 塚本 寛, 渡部 正夫, 高曽 徹, 古川 雅人, 金元 敏明, 溝田 武人, 日本機械学會誌, 111, 1077, 662, 667, 05 Aug. 2008
一般社団法人日本機械学会, JapaneseB11 A Numerical Analysis of Liquid Film Formation on a Rotating Disk
MAEDA Daisuke, IWASAKI Tatsuya, WATANABE Masao, SANADA Toshiyuki, 日本機械学会九州支部講演論文集, 2008, 61, 35, 36, 19 Mar. 2008
The Japan Society of Mechanical Engineers, Japanese229 Diffusion transport phenomena in engineered cartilage
WATANABE Shohei, KITAJIMA Yosuke, NOBAYASHI Makoto, WATANABE Masao, MURAKAMI Teruo, SAWAE Yoshinori, バイオエンジニアリング講演会講演論文集, 2007, 20, 295, 296, 24 Jan. 2008
The Japan Society of Mechanical Engineers, Japanese125 Numerical Study of Blood Flow in the Hepatic Portion of the Inferior Vena Cava on Budd-Chiari Syndrome
MATSUBARA Mizuho, WATANABE Masao, WATANABE Satoshi, KONISHI Kozo, HASHIZUME Makoto, バイオエンジニアリング講演会講演論文集, 2007, 20, 257, 258, 24 Jan. 2008
The Japan Society of Mechanical Engineers, Japanese102 Observation of Capillary Vessel Blood Flow by High Speed Video Capillaroscopy
IRIBE Masaki, KURODA Hiroaki, NAKAMURA Yuki, MATSUBARA Mizuho, WATANABE Masao, SANADA Toshiyuki, バイオエンジニアリング講演会講演論文集, 2007, 20, 3, 4, 24 Jan. 2008
The Japan Society of Mechanical Engineers, JapanesePropagation of Nonlinear Wave in Liquid Containing Encapsulated Microbubbles
Kanagawa Tetsuya, Yano Takeru, Watanabe Masao, Fujikawa Shigeo, 日本流体力学会年会講演論文集, 2008, 306, 306, 2008
One-dimensional nonlinear waves in a liquid containing a number of spherical microbubbles are theoretically studied on the basis of a two-fluid model equations. The set of averaged equations consists of conservation laws of mass and momentum in gas and liquid phases, and the equation of motion of bubble wall. The compressibility of liquid phase is taken into account in the conservation laws and the equation of bubble wall motion, and this leads to the wave attenuation due to bubble oscillations. By using the method of multiple scales, Korteweg-de Vries-Burgers equation can be derived. The properties of the equation are discussed and compared to previous results based on different models on bubbly liquids., 日本流体力学会, Japanese門脈血行異常症に関する調査研究 バッドキアリ症候群機序解明のためのイメージベースドCFDによる流体力学的考察
橋爪誠, 渡部正夫, 松原瑞浦, 小西晃造, 門脈血行異常症調査研究班 平成19年度研究報告書, 34-36, 2008
JapaneseA215 High Speed Video Capillaroscopy and Image Analysis
KURODA Hiroaki, IRIBE Masaki, NAKAMURA Yuki, MATSUBARA Mizuho, SANADA Toshiyuki, WATANABE Masao, Proceedings of the ... JSME Conference on Frontiers in Bioengineering, 2007, 18, 105, 106, 05 Oct. 2007
The Japan Society of Mechanical Engineers, JapaneseA218 Image-based CFD of blood flow field in the hepatic portion of the inferior vena cava on Budd-Chiari syndrome
MATSUBARA Mizuho, WATABANE Masao, WATANABE Satoshi, KONISHI Kozo, HASHIZUME Makoto, Proceedings of the ... JSME Conference on Frontiers in Bioengineering, 2007, 18, 111, 112, 05 Oct. 2007
The Japan Society of Mechanical Engineers, JapaneseA209 Diffusion process and tissue development in cultured cartilage
KITAJIMA Yosuke, WATANABE Shohei, NOBAYASHI Makoto, SAWAE Yoshinori, MURAKAMI Teruo, WATABANE Masao, Proceedings of the ... JSME Conference on Frontiers in Bioengineering, 2007, 18, 93, 94, 05 Oct. 2007
The Japan Society of Mechanical Engineers, Japanese医療と画像処理 高速度ビデオ毛細血管顕微鏡 非侵襲ヒト微小循環ループ内赤血球速度計測と血管形状認識
WATANABE MASAO, KURODA HIROAKI, IRIBE MASAKI, MATSUBARA MIZUHO, FURUE MASUTAKA, SANADA TOSHIYUKI, 画像ラボ, 18, 9, 59, 64, 01 Sep. 2007
日本工業出版, Japanese313 Segmentation and image-based CFD on Budd-Chiari syndrome
MATSUBARA Mizuho, WATABANE Masao, WATANABE Satoshi, KONISHI Kozo, HASHIZUME Makoto, バイオエンジニアリング講演会講演論文集, 2006, 19, 76, 77, 06 Jan. 2007
The Japan Society of Mechanical Engineers, Japanese601 Tissue development and transport phenomena in a regenerated cartilage
KITAJIMA Yousuke, SUGINO Shoichi, WATANABE Masao, SAWAE Yoshinori, SANADA Toshiyuki, MURAKAMI Teruo, バイオエンジニアリング講演会講演論文集, 2006, 19, 198, 199, 06 Jan. 2007
The Japan Society of Mechanical Engineers, Japanese234 On the image analysis of high-speed video capillaroscopy
KURODA Hiroaki, MATSUBARA Mizuho, IRIBE Masaaki, SANADA Toshiyuki, WATANABE Masao, バイオエンジニアリング講演会講演論文集, 2006, 19, 292, 293, 06 Jan. 2007
The Japan Society of Mechanical Engineers, Japaneseバッドキアリ症候群発症機序解明に向けた血管形状セグメンテーションとモデル構築
HASHIZUME MAKOTO, WATANABE MASAO, WATANABE SATOSHI, MATSUBARA MIZUHO, KONISHI KOZO, YAMAGUCHI SHOHEI, YOSHIDA DAISUKE, INAFUKU HITOSHI, KUNIYOSHI YUKIO, 門脈血行異常症調査研究班 平成18年度研究報告書, 29, 34, 2007
Japanese1607 Non-axisymmetric Bubble motion and Wake Structure(1)
ONO Tomoki, SANADA Toshiyuki, Sugihara Keiji, SHIROTA Minori, WATANABE Masao, Fluids engineering conference ..., 2006, "1607, a", 28 Oct. 2006
The Japan Society of Mechanical Engineers, Japanese1607 Non-axisymmetric Bubble motion and Wake Structure(2)
ONO Tomoki, SANADA Toshiyuki, Sugihara Keiji, SHIROTA Minori, WATANABE Masao, Fluids engineering conference ..., 2006, "1607, 1"-"1607-4", 28 Oct. 2006
Wake structure of zigzagging or spiraling motion of free rising bubbles was experimentally investigated. Single bubbles were generated in a silicone oil pooi and the wake structure was observed by using stereo high-speed video cameras. As results, a pair of vortex filaments, which is referred to as double-threaded type wake, was observed in the wake of a bubble rising in non-axisymmetry. Periodical generation of horse-shoe type vortices were observed when the bubbles rose with shape oscillations., The Japan Society of Mechanical Engineers, JapaneseG805 Shape and terminal velocity of a single bubble in superpurified water(2)
SUGIHARA Keiji, ONO Tomoki, SATO Ayaka, SHIROTA Minori, SANADA Toshiyuki, WATANABE Masao, Fluids engineering conference ..., 2006, "G805, 1"-"G805-4", 28 Oct. 2006
We experimentally studied the behavior of a single bubble in superpurified water. We developed the apparatus that can maintain the purity of water during the experiment. The apparatus is equipped with the measurement system for the resistance and TOC value of water so that we can quantitatively evaluate the purity of water. We investigated the critical Reynolds number over which the rising motion of bubble changed from rectangular to zigzag or spiral. We found out the critical Reynolds number was 660 for a bubble in superpurified water. We also compared the experimental results for terminal rise velocity and drag coefficient with the theoretical value for ellipsoidal bubble obtained in the limit of potential flow theory. For small bubbles, experimental values of the terminal velocity and drag coefficient were in good agreement with theoretical ones. For large bubbles, however, experimental values and theoretical ones had the relative deviation of about 8% in the terminal velocity and drag coefficient. This is because the bubble shape shows a deviation from fore-aft symmetry., The Japan Society of Mechanical Engineers, JapaneseG805 Shape and terminal velocity of a single bubble in superpurified water(1)
SUGIHARA Keiji, ONO Tomoki, SATO Ayaka, SHIROTA Minori, SANADA Toshiyuki, WATANABE Masao, Fluids engineering conference ..., 2006, "G805, a", 28 Oct. 2006
The Japan Society of Mechanical Engineers, Japanese306 High Speed Video Capillaroscopic Analysis of Human Capillary Vessel Blood Flow(1)
Watanabe Masao, Sanada Toshiyuki, Sawae Yoshinori, Matsubara Mizuho, Kuroda Hiroaki, Furue Masutaka, Fluids engineering conference ..., 2006, "306, a", 28 Oct. 2006
The Japan Society of Mechanical Engineers, Japanese306 High Speed Video Capillaroscopic Analysis of Human Capillary Vessel Blood Flow(2)
Watanabe Masao, Sanada Toshiyuki, Sawae Yoshinori, Matsubara Mizuho, Kuroda Hiroaki, Furue Masutaka, Fluids engineering conference ..., 2006, "306, 1"-"306-4", 28 Oct. 2006
Human blood flows are highly susceptible to physical and health conditions. Hence quantitative evaluation of blood flow helps the physical check up of individuals. However, the most convenient method is taking a blood sample, which can only examine ex vivo blood condition. We developed digital high speed video capillaroscopy to observe the capillary loops of blood vessels in the finger skin nail fold, of which blood flow can be easily visualized. We discuss the optimal selection of both light source and finger holder, in order to obtain images with both clearer contrast and less blur. We found that the combination of both the halogen light with focusing attachment and brush holder provides satisfactory results with qualitative evaluation by using image processing tools of MATLAB., The Japan Society of Mechanical Engineers, JapaneseHow far does wind force go? 19) Support of CFD to wind turbine performance measurement.
SHIROTA NO, SANADA TOSHIYUKI, MATSUSHITA DAISUKE, HARA YOSHINORI, WATANABE MASAO, MATSUMIYA HIKARU, ターボ機械, 34, 9, 568, 571, 10 Sep. 2006
日本工業出版, JapaneseD23 Measurements of Wind Velocity into a Wind Turbine on Complex Terrain with CFD
SHIROTA Minori, FUJINO Masatoshi, SANADA Toshiyuki, WATANABE Masao, MATSUMIYA Hikaru, 日本機械学会九州支部講演論文集, 2006, 59, 105, 106, Mar. 2006
The Japan Society of Mechanical Engineers, JapaneseD14 Bubble Wake Visualization by using Photochromic Dye
ONO Tomoki, SATO Shinsuke, SHIROTA Minoro, SANADA Toshiyuki, WATANABE Masao, 日本機械学会九州支部講演論文集, 2006, 59, 97, 98, Mar. 2006
The Japan Society of Mechanical Engineers, Japanese305 Blood flow simulation on Budd-Chiari syndrome
MATSUBARA Mizuho, WATABANE Masao, WATANABE Satoshi, HASHIZUME Makoto, KONISHI Kozo, バイオエンジニアリング講演会講演論文集, 2005, 18, 147, 148, 12 Jan. 2006
The Japan Society of Mechanical Engineers, Japanese214 Visualization of tissue structure and transport phenomena in regenerated articular cartilage
SUGINO Shouichi, HAARI Kenta, WATANABE Masao, SAWAE Yoshinori, SANADA Toshiyuki, MURAKAMI Teruo, バイオエンジニアリング講演会講演論文集, 2005, 18, 87, 88, 12 Jan. 2006
The Japan Society of Mechanical Engineers, Japanese医用画像解析及び流体力学的手法によるバッドキアリ症候群発症機序の解明
WATANABE MASAO, MATSUBARA MIZUHO, WATANABE SATOSHI, KONISHI KOZO, YAMAGUCHI SHOHEI, HASHIZUME MAKOTO, INAFUKU HITOSHI, KUNIYOSHI YUKIO, 門脈血行異常症調査研究班 平成17年度研究報告書, 36, 41, 2006
JapanesePreliminary experience with minimally invasive video-assisted surgery for thymic diseases, including myasthenia gravis, through a horizontal ministernotomy
M Watanabe, R Yozu, K Kobayashi, JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY, 130, 3, 912, +, Sep. 2005
MOSBY-ELSEVIER, English, Others1015 Bouncing and Coalescence of a pair of Bubbles Rising Side by Side
SUGIHARA Keiji, SATO Shinsuke, SANADA Toshiyuki, WATANABE Masao, FUKANO Tohru, 日本機械学会九州支部講演論文集, 2005, 58, 387, 388, Mar. 2005
The Japan Society of Mechanical Engineers, Japanese901 On the boundary condition of lattice Boltzmann Method
UEZONO Daisuke, SANADA Toshiyuki, WATANABE Masao, MATSUKUMA Yosuke, 日本機械学会九州支部講演論文集, 2005, 58, 323, 324, Mar. 2005
The Japan Society of Mechanical Engineers, JapaneseBehavior of a pair of bubbles rising side by side
SANADA Toshiyuki, SATO Shinsuke, WATANABE Masao, FUKANO Tohru, Fluids engineering conference ..., 2004, 293, 293, 24 Nov. 2004
The Japan Society of Mechanical Engineers, JapaneseIn Vivo Analysis of Human Capillary Vessel Blood Flow and Vessel Shape
Watanabe Masao, Sanada Toshiyuki, Sawae Yoshinori, Furue Masutaka, Fluids engineering conference ..., 2004, 86, 86, 24 Nov. 2004
The Japan Society of Mechanical Engineers, JapaneseStudy on Adsorption on Gas Liquid Interface by Totao Internal Relection Fluorescence
Watanabe Masao, Sawae Yoshinori, Sanada Toshiyuki, Yotsumoto Kiyoshi, Murakami Teruo, Fluids engineering conference ..., 2004, 88, 88, 24 Nov. 2004
The Japan Society of Mechanical Engineers, JapaneseEffects of Chondrocyte Activity on Macro-Scale Transport Phenomena in Regenerated Articular Cartilage Tissue
Watanabe Masao, Sawae Yoshinori, Haari Kenta, Sanada Toshiyuki, Mizuno Shuichi, Murakami Teruo, Fluids engineering conference ..., 2004, 85, 85, 24 Nov. 2004
The Japan Society of Mechanical Engineers, JapaneseContour Segmentation of Three Dimensional Image Using Level Set Method
WATANABE Masao, バイオエンジニアリング講演会講演論文集, 2004, 16, 159, 160, 21 Jan. 2004
The Japan Society of Mechanical Engineers, JapaneseBehaviors of two bubbles rising side by side
NODA Hitomi, SANADA Toshiyuki, WATANABE Masao, FUKANO Tohru, 日本機械学会九州支部講演論文集, 2003, 139, 140, 30 Oct. 2003
The Japan Society of Mechanical Engineers, JapaneseBubble Behaviors and Liquid Flow Structures in Single Bubble Chain : Liquid Jet Development by Single Bubble
SANADA Toshiyuki, WATANABE Masao, FUKANO Tohru, Fluids engineering conference ..., 2003, 21, 21, 18 Sep. 2003
The Japan Society of Mechanical Engineers, JapaneseLevel Set Based Integration of Segmentation and Computational Fluid Dynamics for Flow Correction in Phase Contrast Angiography.
Masao Watanabe, Ron Kikinis,Carl-Fredrik Westin, Medical Image Computing and Computer-Assisted Intervention - MICCAI 2002, 5th International Conference, Tokyo, Japan, September 25-28, 2002, Proceedings, Part II, 10, 405, 412, 2002, [Peer-reviewed]
Springer416 Effect of generation frequency and bubble diameter on the behavior of single bubble train
SANADA Toshiyuki, WATANABE Masao, FUKANO Tohru, 日本機械学会九州支部講演論文集, 2001, 145, 146, 12 Oct. 2001
The Japan Society of Mechanical Engineers, JapaneseExperimental Study on Contact and Coalescence of a Pair of Bubbles under Micro Gravity Conditons.
WATANABE MASAO, ONIZUKA RYUJI, FUKANO TOORU, 九州大学工学集報, 74, 3, 199, 206, 30 May 2001
Kyushu University, Japanese機械工学年鑑(1999年)流体工学 1. まえがき 2. 非圧縮流れ 3. 圧縮性流れ 4. 混相流 5. 流体機械要素 6. 特殊流体 7. 流体計測 8. 数値流体力学 9. 油空圧技術 10. 水力機械 11. 空気機械
深野 徹, 西 道弘, 田中 和博, 高曽 徹, 宮里 義昭, 青木 俊之, 佐田富 道雄, 富田 侑嗣, 渡邉 聡, 塚本 寛, 児玉 好雄, 大庭 英樹, 半田 太郎, 青木 俊之, 半田 太郎, 益田 光治, 片野田 洋, 益田 光治, 速水 洋, 古川 雅人, 渡部 正夫, 古川 明徳, 井戸 章雄, 坂元 篤, 村井 謙介, 伊高 英彦, 高津 恭, 日本機械学会論文集. B編, 66, 648, 1922, 1935, 25 Aug. 2000
"6・4 希薄流体 / 片野田洋, 益田光治 ", 日本機械学会, JapaneseReport of The 2nd Organized Multiphase Flow Forum'98-Fukuoka : New EFD for Multiphase Flow
MURAI Yuichi, WATANABE Masao, HOSOKAWA Shigeo, FUJIKAWA Shigeo, 混相流 = Japanese journal of multiphase flow, 13, 1, 61, 62, 15 Mar. 1999
JapaneseOscillation-Induced Heat-Transport (Thermoacoustic) Phenomena and Its Application to Thermal Equipments. Linear and Nonlinear Processes in Thermoacoustic Prime Movers. Research Topics in United States.
WATANABE MASAO, 伝熱研究, 36, 142, 69, 72, Jul. 1997
日本伝熱学会, JapaneseNumerical simulation on a bubble motion with full N-S equations.
MATSUMOTO YOICHIRO, WATANABE MASAO, TAKEMURA FUMIO, 東京大学工学部総合試験所年報, 47, 47, 167, 172, Sep. 1988
東京大学工学部総合試験所, JapaneseNonlinear oscillation of gas bubble with consideration of internal condition.
MATSUMOTO YOICHIRO, WATANABE MASAO, 東京大学工学部総合試験所年報, 46, 46, 263, 268, Sep. 1987
東京大学工学部総合試験所, JapaneseLectures, oral presentations, etc.
- 気液界面における速度分布関数の非平衡性が蒸気の流れに与える影響
KON MISAKI, KOBAYASHI KAZUMICHI, WATANABE MASAO
日本物理学会講演概要集(CD-ROM), 24 Mar. 2015, Japanese - 生体光イメージングのためのヒト頸部内光伝播モデルの構築
FUJII HIROYUKI, OKAWA SHIMPEI, NADAMOTO KEN, OKADA EIJI, YAMADA YUKIO, HOSHI YOKO, WATANABE MASAO
バイオエンジニアリング講演会講演論文集, 08 Jan. 2015, Japanese - アルゴン‐ネオン二成分系における気体論境界条件に関する分子動力学シミュレーション
SASAKI KIYOFUMI, KON MISAKI, KOBAYASHI KAZUMICHI, FUJII HIROYUKI, WATANABE MASAO
数値流体力学シンポジウム講演論文集(CD-ROM), 2015, Japanese - 平均場運動論に基づく非平衡蒸発・凝縮下の気液界面における蒸発流束の評価
KON MISAKI, KOBAYASHI KAZUMICHI, WATANABE MASAO
混相流シンポジウム講演論文集(CD-ROM), 2015, Japanese - 真空容器内での高速液滴衝突により発生する液膜流れの観察
KATO MASAYA, YAMAGUCHI YOHEI, KOBAYASHI KAZUMICHI, WATANABE MASAO
混相流シンポジウム講演論文集(CD-ROM), 2014, Japanese - エタノール液滴と固体壁の衝突における周囲雰囲気の影響
SASAGAWA YUUMA, WATANABE MASAO, KOBAYASHI KAZUMICHI
混相流シンポジウム講演論文集(CD-ROM), 2014, Japanese - 縮小・拡大ノズルを用いた液滴噴霧洗浄法に関する数値解析
SAITO IKKI, KAWAHARA JUN'YA, KOBAYASHI KAZUMICHI, WATANABE MASAO
混相流シンポジウム講演論文集(CD-ROM), 2014, Japanese - ナノ液滴の衝突によって発生する液膜流れに関する分子動力学計算
KONNO KAZUKI, FUJII HIROYUKI, KOBAYASHI KAZUMICHI, WATANABE MASAO
数値流体力学シンポジウム講演論文集(CD-ROM), 2014, Japanese - 非平衡気液界面における気体論境界条件の液体温度依存性に関する数値解析
KON MISAKI, KOBAYASHI KAZUMICHI, WATANABE MASAO
数値流体力学シンポジウム講演論文集(CD-ROM), 2014, Japanese - Enskog‐Vlasov方程式による気液界面の気体論境界条件に関する数値シミュレーション
KOBAYASHI KAZUMICHI, KON MISAKI, OHASHI KOTARO, WATANABE MASAO
日本機械学会年次大会講演論文集(CD-ROM), 07 Sep. 2013, Japanese - アルゴン‐ネオン系におけるアルゴン液体の蒸発に関する分子動力学解析
HORI KAZUMASA, YAHAGI TAKATO, TAKEUCHI SHINNOSUKE, YAGUCHI HISAO, KOBAYASHI KAZUMICHI, WATANABE MASAO
日本機械学会年次大会講演論文集(CD-ROM), 07 Sep. 2013, Japanese - Enskog‐Vlasov方程式による温度差のある二液膜を用いた非平衡蒸発・凝縮現象の数値解析
KON MISAKI, KOBAYASHI KAZUMICHI, WATANABE MASAO
日本物理学会講演概要集, 26 Aug. 2013, Japanese - 分子気体論に基づく相変化を伴う気液界面境界条件の流体力学解析への適用手法の検討
JIMBO YOSHINORI, KOBAYASHI KAZUMICHI, WATANABE MASAO
数値流体力学シンポジウム講演論文集(CD-ROM), 2013, Japanese - 固体壁への液滴の衝突により発生するスプラッシュ形成過程の観察
NISHIZAWA HIROKI, KATO MASAYA, UEMURA RYOICHI, KOBAYASHI KAZUMICHI, WATANABE MASAO, SANADA TOSHIYUKI
混相流シンポジウム講演論文集(CD-ROM), 2013, Japanese - 衝撃波管実験と分子気体力学解析による広範囲の非平衡凝縮状態におけるエタノール蒸気の凝縮係数に関する研究
WATANABE YUSUKE, KATAHIRA KEISUKE, KOBAYASHI KAZUMICHI, WATANABE MASAO
混相流シンポジウム講演論文集(CD-ROM), 2013, Japanese - 縮小・拡大ノズル内を加速する液滴噴霧流の数値シミュレーション
SAITO IKKI, KAWAHARA JUN'YA, TAMURA TOSHIYUKI, KOBAYASHI KAZUMICHI, WATANABE MASAO
混相流シンポジウム講演論文集(CD-ROM), 2013, Japanese - 平均場運動論による温度の異なる2つの液膜間での定常蒸発・凝縮の数値計算
KON MISAKI, KOBAYASHI KAZUMICHI, WATANABE MASAO
日本伝熱シンポジウム講演論文集(CD-ROM), 2013, Japanese - 洗浄用ノズル内の高速液滴噴霧流の数値解析
TAMURA TOSHIYUKI, KAWAHARA JUN'YA, KOBAYASHI KAZUMICHI, WATANABE MASAO
日本機械学会北海道支部講演会講演概要集, 20 Oct. 2012, Japanese - 平均場運動理論に基づく非平衡凝縮現象の数値シミュレーション
OHASHI KOTARO, KOBAYASHI KAZUMICHI, WATANABE MASAO
数値流体力学シンポジウム講演論文集(CD-ROM), 2012, Japanese - J054032 Molecular Gas Dynamics on Resonant Gas Oscillations Accompanied with Phase Changes at Vapor-Liquid Interface
INABA Masashi, YANO Takeru, WATANABE Masao, KOBAYASHI Kazumichi, FUJIKAWA Shigeo
Mechanical Engineering Congress, Japan, 11 Sep. 2011, Japanese
The resonant gas oscillation excited in a one-dimensional space between an oscillating plate and a planer surface of a thin liquid layer on a quiescent rigid-wall is considered. Vapor flows with evaporation or condensation at the vapor-liquid interface are theoretically studied on the basis of a polyatomic version of Gaussian-BGK Boltzmann equation with a kinetic boundary condition including an evaporation coefficient. - J054033 Numerical Simulations for Couette flows in Dense Gas Based on Enskog Equation
KOBAYASHI Kazumichi, OHASHI Kotarou, INABA Masashi, WATANABE Masao, FUJIKAWA Shigeo
Mechanical Engineering Congress, Japan, 11 Sep. 2011, Japanese
Numerical simulations for Couette flows in a dense gas are conducted based on the Enskog equation. In order to solve the Enskog equation, we use the particle scheme method, which is an extension of the well known DSMC method that is used to solve the Boltzmann equation. The results agree well with the solution of the Boltzmann equation, as the ratio of molecular diameter to the mean free path of the molecules, a/ A, becomes smaller. A thin layer is formed near a solid wall surface as the ratio al A becomes larger. We also find that the slip velocity on the solid surface depends on the ratio al A. - J054031 Measurements of the Evaporation Coefficient of Water Using Sound Resonance Method
NAKAMURA Shigeto, YANO Takeru, KOBAYASHI Kazumichi, WATANABE Masao, FUJIKAWA Shigeo
Mechanical Engineering Congress, Japan, 11 Sep. 2011, Japanese
We propose a new method for measurement of the evaporation coefficient using sound resonance experiment based on a theory of molecular gas dynamics. The evaporation coefficient is one of the parameters contained in the kinetic boundary condition. The evaporation coefficient of water is determined from the pressure amplitude of resonant sound wave in a cylindrical space bounded by a sound source and a vapor-liquid interface. By comparing the pressure amplitude with a linear theory based on molecular gas dynamics, we prove that the evaporation coefficient of water is about 1.0 around 300K. - Enskog方程式を用いた高密度気体のCouette流れに関する数値計算
小林一道, 大橋広太郎, 稲葉匡司, 渡部正夫, 藤川重雄
日本機械学会年次大会講演論文集, 10 Sep. 2011, Japanese - 8I-11 Material transport and tissue development in engineered cartilage model culture under cyclic compression
SAWAE Yoshinori, WATANABE Masao, OMATA Seiji, MURAKAMI Teruo
バイオエンジニアリング講演会講演論文集, 07 Jan. 2011, Japanese - 圧縮負荷を受ける再生軟骨モデル内の物質輸送と組織形成
SAWAE YOSHINORI, WATANABE MASAO, OMATA SEIJI, MURAKAMI TERUO
バイオエンジニアリング講演会講演論文集, 07 Jan. 2011, Japanese - 403 Human Nailfold Capillary Shape Analysis and Red Blood Cell Velocity Measurement
佐野 宏典, 矢口 久雄, 小林 一道, 渡部 正夫, 藤川 重雄
北海道支部講演会講演概要集, 07 Nov. 2010, Japanese - ヒト爪郭部毛細血管の形状解析および赤血球の速度測定
SANO HIRONORI, YAGUCHI HISAO, KOBAYASHI KAZUMICHI, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会北海道支部講演会講演概要集, 07 Nov. 2010, Japanese - 0407 Nonlinear Waves in Liquid Containing Microbubbles Encapsulated by Visco-Elastic Shell
KANAGAWA Tetsuya, WATANABE Masao, YANO Takeru, FUJIKAWA Shigeo
Fluids engineering conference ..., 29 Oct. 2010, Japanese
Nonlinear propagation of pressure waves in an initially quiescent liquid containing non-uniformly distributed spherical microbubbles is theoretically studied on the basis of the method of multiple scales. We focus on almost unidirectional waves propagating mainly in one direction with a weak diffraction or weak focusing to the transverse direction (like a ultrasound beam). Based on a methodology recently proposed by the authors, the KZK type equation, in which the dispersion and the non-uniformity of number density of bubbles are considered, is derived from the basic equations of bubbly flows. - 303 マイクロ液滴噴霧洗浄技術開発のための高速ノズル流動解析(OS3. ナノ・マイクロ熱流動現象(1),オーガナイズドセッション講演)
高橋 広樹, 渡部 正夫, 小林 一道, 藤川 重雄
計算力学講演会講演論文集, 23 Sep. 2010, Japanese - 302 壁面に衝突する高速マイクロ液滴挙動に及ぼす液滴温度の効果(OS3. ナノ・マイクロ熱流動現象(1),オーガナイズドセッション講演)
ユ ヨンゼ, 渡部 正夫, 小林 一道, 藤川 重雄
計算力学講演会講演論文集, 23 Sep. 2010, Japanese - 301 Evaluation of Evaporation Coefficient at Spherical Vapor-Liquid Interface of Nanodroplet
矢口 久雄, 矢野 猛, 渡部 正夫, 藤川 重雄
The Computational Mechanics Conference, 23 Sep. 2010, Japanese - ナノ液滴の球面状気液界面における蒸発係数の評価
YAGUCHI HISAO, YANO TAKERU, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会計算力学講演会論文集(CD-ROM), 22 Sep. 2010, Japanese - 壁面に衝突する高速マイクロ液滴挙動に及ぼす液滴温度の効果
YU YONZE, WATANABE MASAO, KOBAYASHI KAZUMICHI, FUJIKAWA SHIGEO
日本機械学会計算力学講演会論文集(CD-ROM), 22 Sep. 2010, Japanese - マイクロ液滴噴霧洗浄技術開発のための高速ノズル流動解析
TAKAHASHI HIROKI, WATANABE MASAO, KOBAYASHI KAZUMICHI, FUJIKAWA SHIGEO
日本機械学会計算力学講演会論文集(CD-ROM), 22 Sep. 2010, Japanese - Novel Method for Measurement of Evaporation Coefficient
Nakamura Shigeto, Yano Takeru, Kobayashi Kazumichi, Watanabe Masao, Fujikawa Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 09 Sep. 2010, Japanese
We propose a new method for measurement of the evaporation coefficient using nonlinear sound resonance experiment based on a theory of molecular gas dynamics. The evaporation coefficient is determined from the pressure amplitude of second harmonics generated by the nonlinear effect of resonant sound wave in a cylindrical space bounded by a sound source and a gas-liquid interface. To demonstrate the applicability of this method, we conduct a test experiment. As a result, we confirm the increase of second harmonics amplitude caused by the sound resonance. - Weakly Nonlinear Propagation of Sound Beam in Bubbly Liquids
KANAGAWA Tetsuya, WATANABE Masao, YANO Takeru, FUJIKAWA Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 09 Sep. 2010, Japanese
Weakly nonlinear propagation of pressure waves in an initially quiescent liquid containing many small spherical gas bubbles is studied for the case of low frequency and long wavelength. We focus on almost unidirectional waves propagating mainly in one direction with a weak diffraction to the transverse direction (like a ultrasound beam), i.e., weakly two-dimensional waves. On the basis of a methodology recently proposed by ourselves, the KZK equation with a dispersion term is systematically derived from the basic equations of bubbly flows. - Evaporation Coefficient at a Spherical Vapor-Liquid Interface
Yaguchi Hisao, Yano Takeru, Watanabe Masao, Fujikawa Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 09 Sep. 2010, Japanese
Kinetics of phase change at spherical interface between an argon nanodroplet and its vapor is studied by molecular dynamics simulation. The evaporation coefficient is evaluated at spherical control surface around the nanodroplet at 85K, however it depends on not only a radius of the nanodroplet but also that of control surface. Thus we define a new specific control surface, where the mass flux of evaporating molecules from the nanodroplet into vacuum is equal to that from the planar liquid film. The specific surface is found to be in a few nanometers distance from the center of the vapor-liquid transition layer. We adopt this surface as a interface for evaluating evaporation coefficient and successfully determine the evaporation coefficients for argon nanodroplets ranging from 1 to 4nm in radius. As a result, the evaporation coefficient decreases with decreasing in the radius of the nanodroplet. - Weakly Nonlinear Analysis for Resonant Gas Oscillations with Evaporation and Condensation
Inaba Masashi, Yano Takeru, Watanabe Masao, Kobayashi Kazumichi, Fujikawa Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 09 Sep. 2010, Japanese
The behavior of resonant sound waves in a finite one-dimensional space between an oscillating plate (sound source) and a vapor-liquid interface is analyzed by applying the asymptotic theory for Kn<S0507-1-2 Shock-Tube-Deduced Condensation Coefficients of Water and Methanol Vapors near Equilibrium States : Boltzmann-Equation-Assisted Data Analysis
MOURI Shingo, OGASAWARA Toshiki, YAGUCHI Hisao, WATANABE Masao, FUJIKAWA Shigeo
年次大会講演論文集 : JSME annual meeting, 04 Sep. 2010, Japanese
The condensation coefficients of water and methanol, i.e., the ratios of condensation mass flux of vapor molecules to their mass flux colliding on the interface, are evaluated by combining the experiment conducted by a shock tube and the numerical simulation of Gaussian-BGK Boltzmann equation applicable to polyatomic gases. Film condensation occurs on the endwall of vapor filled shock-tube, when a shock wave is reflected at the endwall and the vapor eventually becomes supersaturated there. The formed liquid film grows with the lapse of time. The time evolution in thickness of the liquid film is measured by an optical interferometer, and thereby the growth rate of the film is obtained. The rate is incorporated into the kinetic boundary condition at the interface for the Gaussian-BGK Boltzmann equation, the solution of which is in consequence obtained uniquely. The condensation coefficients in nearequilibrium states for water and methanol are found to be close to those evaluated by molecular dynamics simulations at equilibrium states.S0507-1-1 Nonequilibrium Molecular Dynamics Simulation of Evaporation and Condensation of Nanodroplet
YAGUCHI Hisao, YANO Takeru, WATAnABE Masao, FUJIKAWA Shigeo
年次大会講演論文集 : JSME annual meeting, 04 Sep. 2010, Japanese
Nonequilibrium molecular dynamics simulation is carried out to study weak condensation of argon vapor into its nanodroplet. Temperature of the nanodroplet is kept at 90 K by using the velocity scaling method. The nanodroplet grows steadily ranging from about 3.3 to 3.4 nm in the radius R_m which is defined as the radius of the center of transition layer in density profile. The mass fluxes at the vapor-nanodroplet interface are investigated and condensation coefficient of the nanodroplet is successfully determined. As a result, the condensation coefficient is almost equal to the evaporation coefficient obtained by our previous study. The rate of change of R_m can be predicted by the mass fluxes and evaporation/condensation coefficients within about 16 percent error.ナノ液滴の蒸発・凝縮に関する非平衡分子動力学シミュレーション
YAGUCHI HISAO, YANO TAKERU, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会年次大会講演論文集, 04 Sep. 2010, Japanese衝撃波管実験とボルツマン方程式解析による平衡状態近傍での水蒸気およびメタノール蒸気の凝縮係数決定
MORI SHINGO, OGASAWARA TOSHIKI, YAGUCHI HISAO, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会年次大会講演論文集, 04 Sep. 2010, Japanese気泡を含む液体中における圧力波の非線形解析
KANAGAWA TETSUYA, YANO TAKERU, WATANABE MASAO, FUJIKAWA SHIGEO
日本混相流学会年会講演会講演論文集, Jul. 2010, Japanese水蒸気・水混合噴流低環境負荷洗浄法によるドライエッチング残渣除去
WATANABE MASAO, SANADA TOSHIYUKI, MASHIKO TAKASHI, SEKI AKIKO, HAYASHIDA ATSUSHI
日本混相流学会年会講演会講演論文集, Jul. 2010, Japanese蒸発・凝縮をともなう共鳴音波に関する数値解析
INABA MASASHI, YOSHINAKA RINTARO, WATANABE MASAO, FUJIKAWA SHIGEO, YANO TAKERU
日本混相流学会年会講演会講演論文集, Jul. 2010, Japanese水蒸気・水混合噴流の物理力の実験的評価
MASHIKO TAKASHI, HAYASHIDA ATSUSHI, SANADA TOSHIYUKI, WATANABE MASAO
日本混相流学会年会講演会講演論文集, Jul. 2010, Japanese気泡後部トロイダル渦の抗力への寄与
SHIROTA MINORI, SATO AYAKA, SANADA TOSHIYUKI, WATANABE MASAO
日本混相流学会年会講演会講演論文集, Jul. 2010, Japanese非線形共鳴音波による水の蒸発係数測定
NAKAMURA SHIGETO, INABA MASASHI, WATANABE MASAO, FUJIKAWA SHIGEO, YANO TAKERU
理論応用力学講演会講演論文集, 08 Jun. 2010, Japanese蒸発・凝縮をともなう非線形音波に関する分子気体力学解析
INABA MASASHI, YANO TAKERU, WATANABE MASAO, FUJIKAWA SHIGEO
理論応用力学講演会講演論文集, 08 Jun. 2010, Japanese粘弾性殻付き気泡を含む液体中における非線形波動
KANAGAWA TETSUYA, WATANABE MASAO, YANO TAKERU, FUJIKAWA SHIGEO
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2010, Japanese206 Development of Low-pressure Submerged Water Jet for Organic Compounds Decomposition
中村 謙介, 渡部 正夫, 藤川 重雄
北海道支部講演会講演概要集, 28 Nov. 2009, Japanese有機化合物分解用低圧水中ウォータージェットの開発
NAKAMURA KENSUKE, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会北海道支部講演会講演概要集, 28 Nov. 2009, Japanese1605 Visualization of Nailfold Micro-circulation Using High-speed Video Capillaroscopy
WATANABE Masao, NAKAMURA Yuuki, SANO Hironori, YAGUCHI Hisao
Fluids engineering conference ..., 06 Nov. 2009, Japanese
Capillaroscopy is a "lens" that is able to observe capillary loops of blood vessels in the human finger skin nail fold, of which blood flow can be easily visualized, and has been long used for clinical diagnosis. We have been developing digital high speed video capillaroscopy by integrating to high-speed high-sensitivity video camera with deep-focus zoom lens. We discuss quantitative evaluation of blood velocity in both arteriol and venule of human nailfold microcirculation, using two different methods, namely, plasma gap tracking method and fixed point observation method with correlation.T0501-2-5 Molecular Dynamics Analysis of Temperature Change in Nanodroplet Evaporating into Vacuum
YAGUCHI Hisao, TANAKA Ryoichi, YANO Takeru, WATANABE Masao, FUJIKAWA Shigeo
年次大会講演論文集 : JSME annual meeting, 12 Sep. 2009, Japanese
Molecular dynamics simulations of an argon nanodroplet evaporating into vacuum are carried out to investigate time development of its temperature. Configuration in vaporliquid equilibrium state of the nanodroplet with 3.6 nm in radius at 105 K is adopted as initial configuration of the evaporation. Although the temperature of nanodroplet decreases with time because of the loss of latent heat for evaporation, rapid temperature rise has been observed at about 8.0 ns. Radial distribution function of molecules inside the nanodroplet suggests that phase change from liquid to solid has been occurred. Recovery from the supercooling consequent to release of latent heat for solidification is thought to be cause of this rapid temperature rise.T0501-2-4 Evaluation of Condensation Coefficient of Water in Near-equilibrium State by Shock Tube and Molecular Gas Dynamics
OGASAWARA Toshiki, YAMANO Daigo, WATANABE Masao, FUJIKAWA Shigeo
年次大会講演論文集 : JSME annual meeting, 12 Sep. 2009, Japanese
The condensation coefficient of water, ie., the ratio of condensation mass flux of vapor molecules to incoming mass flux at the interface, is evaluated by combining the experiment conducted by a shock tube and the numerical simulation of Gaussian-BGK Boltzmann equation applicable to polyatomic gases. Film condensation occurs on the endwall of a vaporfilled shock-tube, when a shock wave is reflected at the endwall and the vapor becomes supersaturated there. The formed liquid film grows with the lapse of time. The time evolution in thickness of the liquid film is measured by an optical interferometer, and thereby the growth rate of the film is obtained. The rate is incorporated into the kinetic boundary condition at the interface for the Gaussian-BGK Boltzmann equation, and the unique numerical solution of the vaporliquid system is obtained. Values of condensation coefficient in near equilibrium state are found to be close to that evaluated by molecular dynamics simulations at the equilibrium state.J0201-1-6 Acoustic Characteristics of Ultrasound Propagating in Liquid Containing Lipid Bubbles
IMAI Ryosuke, NAKAGAWA Hiroya, SAKURAI Kousuke, WATANABE Masao, FUJIKAWA Shigeo
年次大会講演論文集 : JSME annual meeting, 12 Sep. 2009, Japanese
In the field of medical engineering, the application of bubbles of nanometer size to Drug Delivery System (DDS) has attracted great attention as the administration of next generation. DDS with bubbles is expected to be a noninvasive clinical treatment. As the transport carrier of DDS, there exists bubble encapsulated in a lipid bilayer, generally called as a lipid bubble. However, dynamic properties of these lipid bubbles are not yet made clear. In this study, acoustic characteristics of lipid bubbles are experimentally investigated. The resonant frequencies of lipid bubbles are evaluated from attenuation of ultrasound pulse propagating through the experimental cell filled with lipid bubble solution. It is found that the attenuation spectrum has two dominant peaks in the frequency range of 1.0 through 14.0 MHz due to the acoustic energy absorbed by lipid bubble with resonant oscillations.Acoustic Characteristics of Ultrasound Propagating in Liquid Containing Lipid Bubbles
IMAI RYOSUKE, NAKAGAWA HIROYA, SAKURAI KOSUKE, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会年次大会講演論文集, 12 Sep. 2009, JapaneseEvaluation of Condensation Coefficient of Water in Near-equilibrium State by Shock Tube and Molecular Gas Dynamics
OGASAWARA TOSHIKI, YAMANO DAIGO, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会年次大会講演論文集, 12 Sep. 2009, JapaneseMolecular Dynamics Analysis of Temperature Change in Nanodroplet Evaporating into Vacuum
YAGUCHI HISAO, TANAKA RYOICHI, YANO TAKERU, WATANABE MASAO, FUJIKAWA SHIGEO
日本機械学会年次大会講演論文集, 12 Sep. 2009, JapaneseEvaluation of Evaporation Coefficient at the Vapor-liquid Interface of Argon Nanodroplet by Molecular Dynamics Method
Yaguchi Hisao, Yano Takeru, Watanabe Masao, Fujikawa Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 02 Sep. 2009, Japanese
Mass fluxes and evaporation coefficients at the interface between an argon nanodroplet and its vapor are investigated by nonequilibrium molecular dynamics (MD) simulations. The simulations are carried out at the temperatures of 85, 90, 95, 100, and 105K with droplet radii ranging from about 1nm to 4nm. The evaporation mass fluxes J_are obtained by MD simulations of evaporation into vacuum and are found to be almost independent of droplet radius at the specified control surface R_ . Since the outgoing mass flux J_ in an equilibrium state becomes large as the droplet radius does small, the evaporation coefficient α_e, defined by the ratio of J_ to J_ , decreases with decrease in the droplet radius. Weakly Nonlinear Propagation of Quasi-Monochromatic Waves in Bubbly Liquids
Kanagawa Tetsuya, Yano Takeru, Watanabe Masao, Fujikawa Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 02 Sep. 2009, Japanese
One-dimensional nonlinear dispersive waves in a liquid containing a number of small spherical gas bubbles are theoretically studied based on a set of two-fluid averaged equations composed of the conservation laws of mass and momentum for gas and liquid phases, and the Keller equation for the bubble dynamics. The liquid compressibility is taken into account, and this leads to the wave attenuation due to bubble oscillations. By using an appropriate scaling of physical parameters and the method of multiple scales, we can derive the nonlinear Schrodinger equation with an attenuation term due to the acoustic radiation and the liquid viscosity. This equation describes a far field of a quasi-monochromatic wave train in the bubbly liquid, which evolves into a slowly modulated wave packet as a result of long range propagation of weakly nonlinear waves with the strong dispersion effect.Molecular Gas Dynamics on Resonant Sound Waves Excited in One-Dimensional Space between Oscillating Plate and Vapor-Liquid Interface
INABA Masashi, YANO Takeru, WATANABE Masao, FUJIKAWA Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 02 Sep. 2009, Japanese
The behavior of resonant sound waves in a finite one-dimensional space between an oscillating plate (sound source) and a vapor-liquid interface is analyzed by applying the asymptotic theory for Kn<30aTJ-5 Molecular Dynamics Study of Vapor-liquid Equilibrium Condition of Nanodroplet
Yaguchi Hisao, Yano Takeru, Watanabe Masao, Fujikawa Shigeo
Meeting abstracts of the Physical Society of Japan, 03 Mar. 2009, Japanese超微小液滴の気液平衡条件に関する分子動力学的研究
YAGUCHI HISAO, YANO TAKERU, WATANABE MASAO, FUJIKAWA SHIGEO
日本物理学会講演概要集, 03 Mar. 2009, Japanese508 Transport Phenomena in Scaffold Gel for Engineered Cartilage
NOBAYASHI Makoto, WATANABE Shouhei, NODA Hiroyuki, SAWAE Yoshinori, WATANABE Masao
バイオエンジニアリング講演会講演論文集, 22 Jan. 2009, Japanese318 Noninvasive Observation of Red Blood Cell Dynamics with High Speed Digital Video Capillaroscopy
NAKAMURA Yuuki, IRIBE Masaki, MATSUBARA Mizuho, WATANABE Masao
バイオエンジニアリング講演会講演論文集, 22 Jan. 2009, Japanese再生軟骨担体ゲル内での物質輸送現象
NOBAYASHI MAKOTO, WATANABE SHOHEI, NODA HIROYUKI, SAWAE YOSHINORI, WATANABE MASAO
バイオエンジニアリング講演会講演論文集, 22 Jan. 2009, Japanese高速度ビデオ毛細血管顕微鏡を用いた非侵襲赤血球動態観察
NAKAMURA YUKI, IRIBE MASAKI, MATSUBARA MIZUHO, WATANABE MASAO
バイオエンジニアリング講演会講演論文集, 22 Jan. 2009, JapanesePropagation of Nonlinear Wave in Liquid Containing Encapsulated Microbubbles
Kanagawa Tetsuya, Yano Takeru, Watanabe Masao, Fujikawa Shigeo
Proceedings, ... meeting of Japan Society of Fluid Mechanics, 04 Sep. 2008, Japanese
One-dimensional nonlinear waves in a liquid containing a number of spherical microbubbles are theoretically studied on the basis of a two-fluid model equations. The set of averaged equations consists of conservation laws of mass and momentum in gas and liquid phases, and the equation of motion of bubble wall. The compressibility of liquid phase is taken into account in the conservation laws and the equation of bubble wall motion, and this leads to the wave attenuation due to bubble oscillations. By using the method of multiple scales, Korteweg-de Vries-Burgers equation can be derived. The properties of the equation are discussed and compared to previous results based on different models on bubbly liquids.337 Advection and Diffusion Transport Phenomena in Engineered Cartilage
NOBAYASHI Makoto, KITAJIMA Yousuke, WATANABE Shouhei, SAWAE Yoshinori, WATANABE Masao
年次大会講演論文集 : JSME annual meeting, 02 Aug. 2008, Japanese
Engineered cartilages are expected to be used for the treatment of cartilage defects. Cartilage tissue is avascular; hence transport phenomena are controlled by diffusion and also advection by so called "pumping mechanism" of tissue. The objective of present paper is to evaluate the contribution of both diffusion and advection in engineered tissue for the control of transport phenomena.703 Evaluation of Red Blood Cell Dynamics with High Speed Digital Video Capillaroscopy
NAKAMURA Yuuki, WATANABE Masao, IRIBE Masaki, MATSUBARA Mizuho
年次大会講演論文集 : JSME annual meeting, 02 Aug. 2008, Japanese
Nailfold video capillaroscopy (NVC) can observe the micro vascular structure non-invasively. We developed NVC by using high speed digital video camera to evaluate both micro vascular structure and red blood cell movement quantitatively The objects of this study are to evaluate the radius distribution of micro vascular by level-set method and also the red blood cell velocity by tracing plasma gap between blood cells.Evaluation of Red Blood Cell Dynamics with High Speed Digital Video Capillaroscopy
NAKAMURA YUKI, WATANABE MASAO, IRIBE MASAKI, MATSUBARA MIZUHO
日本機械学会年次大会講演論文集, 02 Aug. 2008, JapaneseAdvection and Diffusion Transport Phenomena in Engineered Cartilage
NOBAYASHI MAKOTO, KITAJIMA YOSUKE, WATANABE SHOHEI, SAWAE YOSHINORI, WATANABE MASAO
日本機械学会年次大会講演論文集, 02 Aug. 2008, Japanese単一上昇気泡の3次元後流の可視化
KOGA KIYONORI, SATO AYAKA, SHIROTA MINORI, SANADA TOSHIYUKI, WATANABE MASAO
日本混相流学会年会講演会講演論文集, Aug. 2008, Japanese超純水中を上昇する単一気泡の自由界面及び壁面との反発現象
UCHIDA YUSUKE, SATO AYAKA, SHIROTA MINORI, SANADA TOSHIYUKI, WATANABE MASAO
日本混相流学会年会講演会講演論文集, Aug. 2008, JapaneseB11 A Numerical Analysis of Liquid Film Formation on a Rotating Disk
MAEDA Daisuke, IWASAKI Tatsuya, WATANABE Masao, SANADA Toshiyuki
日本機械学会九州支部講演論文集, 19 Mar. 2008, Japanese125 Numerical Study of Blood Flow in the Hepatic Portion of the Inferior Vena Cava on Budd-Chiari Syndrome
MATSUBARA Mizuho, WATANABE Masao, WATANABE Satoshi, KONISHI Kozo, HASHIZUME Makoto
バイオエンジニアリング講演会講演論文集, 24 Jan. 2008, Japanese229 Diffusion transport phenomena in engineered cartilage
WATANABE Shohei, KITAJIMA Yosuke, NOBAYASHI Makoto, WATANABE Masao, MURAKAMI Teruo, SAWAE Yoshinori
バイオエンジニアリング講演会講演論文集, 24 Jan. 2008, JapaneseImage-based CFD of Blood Flow in the Hepatic Portion of the Inferior Vena Cava on Budd-Chiari Syndrome
MATSUBARA MIZUHO, WATANABE MASAO, WATANABE SATOSHI, KONISHI KOZO, YAMAGUCHI SHOHEI, HASHIZUME MAKOTO
日本機械学会年次大会講演論文集, 07 Sep. 2007, JapaneseHigh Speed Video Capillaroscopy and Capillary Vessel Blood Flow
IRIBE MASAKI, KURODA HIROAKI, WATABE MASAO, MATSUBARA MIZUHO, SANADA TOSHIYUKI
日本機械学会年次大会講演論文集, 07 Sep. 2007, JapaneseVisualization of Single Rising Bubble Wake
TAKETOMI YUTA, SATO AYAKA, SHIROTA MINORI, SANADA TOSHIYUKI, WATABE MASAO
日本機械学会年次大会講演論文集, 07 Sep. 2007, Japanese蒸気と水の混合噴流によるレジスト剥離
SANADA TOSHIYUKI, SAITO TAKAYUKI, SHIROTA TSUTOMU, WATABE MASAO, MORITA YOSHINAO, YAMASE MASAO
応用物理学会学術講演会講演予稿集, 04 Sep. 2007, Japanese水蒸気と水の混合噴流によるレジスト剥離・洗浄装置の開発
SANADA TOSHIYUKI, SHIROTA MINORI, WATANABE MASAO, YAMASE MASAO
日本学術会議混相流シンポジウム講演資料集, Jun. 2007, Japanese単一気泡の形状と定常抗力
SATO AYAKA, SHIROTA MINORI, SANADA TOSHIYUKI, WATABE MASAO
日本混相流学会年会講演会講演論文集, Jun. 2007, Japanese超純水中における単一気泡と自由界面との反発現象
UCHIDA YUSUKE, SATO AYAKA, SHIROTA MINORI, SANADA TOSHIYUKI, WATABE MASAO
日本混相流学会年会講演会講演論文集, Jun. 2007, Japanese気泡後部定在渦の可視化
SANADA TOSHIYUKI, SHIROTA TAKA, ONO YUKI, WATABE MASAO
化学工学会年会研究発表講演要旨集, 19 Feb. 2007, Japanese超純水中の気泡挙動
SANADA TOSHIYUKI, SHIROTA TAKA, SUGIHARA KEIJI, WATABE MASAO
化学工学会年会研究発表講演要旨集, 19 Feb. 2007, Japanese高速度ビデオcapillaroscopyとその画像解析
KURODA HIROAKI, MATSUBARA MIZUHO, IRIBE MASAKI, SANADA TOSHIYUKI, WATANABE MASAO
バイオエンジニアリング講演会講演論文集, 06 Jan. 2007, Japaneseバッドキアリ症候群機序解明に向けた血管形状セグメンテーションとモデル構築
MATSUBARA MIZUHO, HOTANABE MASAO, WATANABE SATOSHI, KONISHI KOZO, YAMAGUCHI SHOHEI, HASHIZUME MAKOTO
バイオエンジニアリング講演会講演論文集, 06 Jan. 2007, Japanese再生軟骨における組織形成と輸送現象
KITAJIMA YOSUKE, SUGINO SHOICHI, WATANABE MASAO, SAWAE YOSHINORI, SANADA TOSHIYUKI, MURAKAMI TERUO
バイオエンジニアリング講演会講演論文集, 06 Jan. 2007, JapaneseBubble Wake Visualization by using Photochromic Dye
SANADA TOSHIYUKI, SHIROTA MINORI, ONO TOMOKI, WATANABE MASAO
可視化情報学会論文集(Web), 2007, JapaneseMacro-scale transport phenomena in articular cartilage
SUGINO SHOICHI, KITAJIMA YOSUKE, WATANABE MASAO, SAWAE YOSHINORI, SANADA TOSHIYUKI, MURAKAMI TERUO
日本機械学会年次大会講演論文集, 15 Sep. 2006, JapaneseSite calibration by with the aid of CFD
FUJINO MASATOSHI, SHIROTA MINORI, SANADA TOSHIYUKI, MATSUSHITA DAISUKE, WATANABE MASAO, MATSUMIYA HIKARU
日本機械学会年次大会講演論文集, 15 Sep. 2006, JapaneseFormation of single bubbles controlled with fluctuating gas pressure
SANADA TOYUSHIKI, SHIROTA MINORU, ARATA YASUHIRO, WATANABE MASAO
日本機械学会年次大会講演論文集, 15 Sep. 2006, JapaneseBouncing and Coalescence of a pair of Bubbles in a Quiescent Liquid
SUGIHARA KEIJI, ONO TOMOKI, SHIROTA MINORI, SANADA TOSHIYUKI, WATANABE MASAO
日本機械学会年次大会講演論文集, 15 Sep. 2006, Japanese気体圧力変動を利用した単一微細気泡発生法
SANADA TOSHIYUKI, KIDA NO, WATANABE MASAO
化学工学会秋季大会研究発表講演要旨集(CD-ROM), 16 Aug. 2006, Japanese静止液体中を上昇する2気泡の合体および反発
SANADA TOSHIYUKI, WATANABE MASAO
化学工学会秋季大会研究発表講演要旨集(CD-ROM), 16 Aug. 2006, Japanese高Re数における水平に並んで上昇する2気泡の挙動
SATO AYAKA, SATO SHINSUKE, SHIROTA MINORI, SANADA TOSHIYUKI, WATANABE MASAO
日本混相流学会年会講演会講演論文集, Aug. 2006, Japaneseフォトクロミック染料による気泡後流渦の可視化
ONO TOMOKI, SHIROTA MINORI, SATO SHINSUKE, SANADA TOSHIYUKI, WATANABE MASAO
日本混相流学会年会講演会講演論文集, Aug. 2006, Japanese気体圧力変動を利用した単一微細気泡発生メカニズム
SHIROTA MINORI, SANADA TOSHIYUKI, ARATA YASUHIRO, WATANABE MASAO, KAMEDA MASAHARU
日本混相流学会年会講演会講演論文集, Aug. 2006, JapaneseCFDを援用した複雑地形における風車流入風計測法
SHIROTA MINORI, FUJINO MASATOSHI, SANADA TOSHIYUKI, WATANABE MASAO, MATSUMIYA HIKARU
日本機械学会九州支部講演論文集, Mar. 2006, Japaneseフォトクロミック染料による気泡後流の可視化
ONO TOMOKI, SATO SHINSUKE, SHIROTA MINORO, SANADA TOSHIYUKI, WATANABE MASAO
日本機械学会九州支部講演論文集, Mar. 2006, Japanese再生関節軟骨組織形成と輸送現象の可視化
SUGINO SHOICHI, HAARI KENTA, WATANABE MASAO, SAWAE YOSHINORI, SANADA TOSHIYUKI, MURAKAMI TERUO
バイオエンジニアリング講演会講演論文集, 12 Jan. 2006, Japaneseバッドキアリ症候群における血流シミュレーション
MATSUBARA MIZUHO, WATANABE MASAO, WATANABE SATOSHI, HASHIZUME MAKOTO, KONISHI KOZO
バイオエンジニアリング講演会講演論文集, 12 Jan. 2006, JapaneseNon-axisymmetric Bubble motion and Wake Structure
ONO TOMOKI, SANADA TOSHIYUKI, SUGIHARA KEIJI, SHIROTA MINORI, WATANABE MASAO
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2006, JapaneseShape and terminal velocity of a single bubble in superpurified water
SUGIHARA KEIJI, ONO TOMOKI, SATO AYAKA, SHIROTA MINORI, SANADA TOSHIYUKI, WATANABE MASAO
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2006, JapaneseHigh Speed Video Capillaroscopic Analysis of Human Capillary Vessel Blood Flow
WATANABE MASAO, SANADA TOSHIYUKI, SAWAE YOSHINORI, MATSUBARA MIZUHO, KURODA HIROAKI, FURUE MASUTAKA
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2006, Japanese高島町における数値サイトキャリブレーションの試み
FUJINO MASATOSHI, SANADA TOSHIYUKI, MATSUSHITA DAISUKE, UCHIDA TAKANORI, WATANABE MASAO, MATSUMIYA HIKARU
風力エネルギー利用シンポジウム, Nov. 2005, Japanese水平に並んで上昇する2気泡の反発現象
SANADA TOSHIYUKI, SUGIHARA KEIJI, WATABE MASAO, FUKANO TOORU
日本混相流学会年会講演会講演論文集, Aug. 2005, Japanese培養軟骨細胞による組織構造形成と力学的機能発現
SAWAE YOSHINORI, ISHIYAMA SHO, HANAKI AKIHIRO, WATANABE MASAO, MURAKAMI TERUO
日本ME学会大会論文集, 25 Apr. 2005, Japanese水平に並んで上昇する2気泡の合体および反発
SUGIHARA KEIJI, SATO SHINSUKE, SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU
日本機械学会九州支部講演論文集, Mar. 2005, Japanese格子ボルツマン法の境界条件に関する検討
UEZONO DAISUKE, SANADA TOSHIYUKI, WATANABE MASAO, MATSUKUMA YOSUKE
日本機械学会九州支部講演論文集, Mar. 2005, Japaneseヒト毛細血管のin vivo血流・形状観察
SANADA TOSHIYUKI, WATANABE MASAO, SAWAE YOSHINORI, FURUE MASUTAKA
バイオエンジニアリング講演会講演論文集, 21 Jan. 2005, Japanese再生関節軟骨内輸送現象の可視化(細胞活動の影響)
WATANABE MASAO, SAWAE YOSHINORI, SANADA TOSHIYUKI, HAARI KENTA, MURAKAMI TERUO
バイオエンジニアリング講演会講演論文集, 21 Jan. 2005, JapaneseViscosity Effects on Bouncing and Coalescence of a Pair of Bubbles
SANADA TOSHIYUKI, SATO AYAKA, WATANABE MASAO, FUKANO TOORU
日本機械学会年次大会講演論文集, 04 Sep. 2004, Japanese単一ノズルから連続して発生させた2気泡の挙動に関する研究
SANADA TOSHIYUKI, WATANABE MASAO, ISHIDA DAIJIRO, FUKANO TOORU
日本混相流学会年会講演会講演論文集, Aug. 2004, JapaneseIn Vivo Analysis of Human Capillary Vessel Blood Flow and Vessel Shape
WATANABE MASAO, SANADA TOSHIYUKI, SAWAE YOSHINORI, FURUE MASUTAKA
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2004, Japanese水平に並んで上昇する2気泡の挙動に関する研究
SANADA TOSHIYUKI, SATO SHINSUKE, WATANABE MASAO, FUKANO TOORU
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2004, JapaneseEffects of Chondrocyte Activity on Macro-Scale Transport Phenomena in Regenerated Articular Cartilage Tissue
WATANABE MASAO, SAWAE YOSHINORI, HAARI KENTA, SANADA TOSHIYUKI, MIZUNO CHUICHI, MURAKAMI TERUO
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2004, JapaneseStudy on Adsorption on Gas-Liquid Interface by Totao Internal Relection Fluorescence Microscopy
WATANABE MASAO, SAWAE YOSHINORI, SANADA TOSHIYUKI, YOTSUMOTO KIYOSHI, MURAKAMI TERUO
日本機械学会流体工学部門講演会講演論文集(CD-ROM), 2004, Japanese横に並んだ上昇2気泡の挙動に関する研究
NODA HITOMI, SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU
日本機械学会九州支部地方講演会講演論文集, 01 Nov. 2003, JapaneseBubble Behaviors and Liquid Flow Structures in Single Bubble Chain(Liquid Jet Development by Single Bubble)
SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU
日本機械学会流体工学部門講演会講演論文集, 19 Sep. 2003, Japanese単一気泡列中の気泡挙動および周囲液体流れ場構造 (気泡列による液ジェットの生成)
SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU
日本機械学会流体工学部門講演会講演論文集, 18 Sep. 2003, Japanese自由界面での単一気泡の合体および反発に関する研究
SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU
日本混相流学会年会講演会講演論文集, Jul. 2003, Japaneseレベルセット法を用いたCFDによるMRアンギオグラフィーの修正
WATANABE MASAO, KIKINIS R, WESTIN C-F
数値流体力学シンポジウム講演論文集, 16 Dec. 2002, Japanese自由界面近傍における単一上昇気泡の合体・反発に及ぼす粘性の影響
SANADA TOSHIYUKI, WATANABE MASAO, YUDA TOMOHIRO, FUKANO TOORU
数値流体力学シンポジウム講演論文集, 16 Dec. 2002, Japanese単一ノズルから発生する気泡列による周囲流体の挙動に関する研究
SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU
日本混相流学会年会講演会講演論文集, Jul. 2002, Japanese単独のノズルから発生する気泡列の挙動に及ぼす発生頻度および気泡径の影響
SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU
日本機械学会九州支部地方講演会講演論文集, 12 Oct. 2001, Japanese単独のノズルから発生する気泡列の挙動に及ぼす発生頻度の影響
SANADA TOSHIYUKI, WATANABE MASAO, FUKANO TOORU, KARIYAZAKI AKIRA
日本混相流学会年会講演会講演論文集, Jul. 2001, Japanese二つの気液界面が互いに近づく時の界面間の流体の挙動
ONIZUKA RYUJI, WATANABE MASAO, FUKANO TOORU
日本混相流学会年会講演会講演論文集, Jul. 2000, JapaneseNumerical Analysis on Motion of a Pair of Rising Bubbles by Using Finite Element Method with Time Dependent Non-Structured Deforming Grid.
WATANABE MASAO, SHRESTHA R, FUKANO TOORU
日本機械学会計算力学講演会講演論文集, Nov. 1998, JapaneseNumerical Analysis on the In-line Motion of a Pair of Rising Deforming Bubbles.
WATANABE MASAO, SHRESTHA R, FUKANO TOORU
日本機械学会流体工学部門講演会講演論文集, Aug. 1998, Japanese数値シミュレーションを用いた気流を伴う水平矩形管内薄膜流に関する研究
INATOMI TAKANARI, FUKANO TOORU, WATANABE MASAO
混相流シンポジウム講演論文集, Jul. 1998, Japanese時間依存非構造変形格子を用いた気泡運動の有限要素法による数値計算
WATANABE MASAO, SHRESTHA R, FUKANO TOORU
混相流シンポジウム講演論文集, Jul. 1998, JapaneseWeakly Nonlinear Analysis on Translational Motions of Two Bubbles in Periodically Driven Pressure Field.
WATANABE MASAO
日本機械学会計算力学講演会講演論文集, Jul. 1997, JapaneseA novel way of computing heat transfer in bubble dynamics.
WATANABE MASAO, MATSUMOTO YOICHIRO
日本機械学会計算力学講演会講演論文集, Jul. 1997, JapaneseAffiliated academic society
Research Themes
- Evaporation coefficient of nanoparticle suspension
Grants-in-Aid for Scientific Research
01 Apr. 2024 - 31 Mar. 2028
小林 一道, 藤井 宏之, 渡部 正夫
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 24K00797 - 蒸気中の液滴固体面衝突における凝縮効果によるsplash発生抑制機序の解明
科学研究費助成事業
01 Apr. 2024 - 31 Mar. 2026
渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之
日本学術振興会, 基盤研究(B), 北海道大学, 23K26027 - Elucidation of non-equilibrium phase change at gas-liquid interface mechanism for mixture gas and its application to molecular multi-phase fluid dynamics
Grants-in-Aid for Scientific Research
01 Apr. 2020 - 31 Mar. 2023
小林 一道, 藤井 宏之, 渡部 正夫
本提案研究は,混合気体に接した気液界面における気体論境界条件を構築し,様々な分野に本研究成果を展開することである.2021年度は主に以下の3つの研究を行った.
1.分子計算(分子運動論および分子動力学シミュレーション)を用いて,非平衡気液界面における気体論境界条件の構築を行った.その結果,気体論境界条件に含まれる二つの未知パラメータ(蒸発係数および凝縮係数)を決定した.本結果より,非平衡気液界面における蒸発係数と凝縮係数の値は,平衡状態および非平衡状態においてほぼ変わらないことが明らかとなった.これにより,初期液体温度などの条件にもよるが,平衡状態の蒸発係数および凝縮係数を求めておけば気体論境界条件を構築できることが示唆された.
2.分子動力学解析を用いて,固体壁と液体に挟まれた気体のクエット流れについて解析を行った.この研究より,気液界面における気体論境界条件の位置を検証した.本研究より,1の研究で指定していた気体論境界条件の位置は妥当であることが示唆された.また,高クヌーセン数流れになるほど,気液界面の境界条件が平衡状態の関数形から異なることが示唆された.これについてはさらなる検討が必要である.
3.分子動力学解析を用いて,混合液体(エタノール・イソオクタン)の蒸発について検証した.分子動力学計算を用いてエタノール・イソオクタンの気液平衡系を作り出し,1の研究で提案した方法によって,液体から蒸発する分子の成分について調べた.その結果,エタノールの濃度が低い混合液体においても,蒸発するエタノール分子の割合は高くなることが示された.今後はこの知見を用いて実験結果を整理する予定である.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 20K04277 - Influence of the interference effects on radiative transfer in dense colloidal suspensions
Grants-in-Aid for Scientific Research
01 Apr. 2020 - 31 Mar. 2023
藤井 宏之, 西村 吾朗, 渡部 正夫, 小林 一道
本研究の目的は、「生体を模擬した高密度なコロイド溶液に対して、輻射(ふくしゃ)の干渉効果を組み込んだ輻射輸送モデル(輸送モデル)を新たに構築した上で、干渉効果が及ぼす光伝播への影響を明らかにすること」である。生体光イメージングや光治療において、生体内の光伝播を定量的に把握することが必要であり、光を輻射と捉えた輸送モデルが活用されている。しかし、従来の輸送モデルには、生体のような高密度な散乱媒体において重要となる干渉効果が考慮されていない。本研究では電磁波の散乱理論より干渉効果を考慮した散乱特性を計算し、輸送モデルに組み込んだ上で光強度の時間分解波形を数値計算する。また、短パルスレーザー光源による光強度計測も実施する。干渉効果が光伝播へ影響を及ぼす時空間スケールについて、散乱係数などで表される無次元数を用いて解析し、理論、数値計算、実験より体系的に明らかにする。この目的を達成するため、本年度は以下の3項目について研究を実施した。
1.光散乱特性を簡潔に記述するモデル式を開発した。モデル式により、単一散乱の寄与と干渉効果の寄与を分離して評価することに初めて成功した。
2.分担研究者の西村吾朗助教の波長可変の光計測システムを利用して、コロイド溶液(脂質エマルジョン)において、濃度20%まで21条件、720 nmから860 nmまでの6条件で光計測を実施した。光計測データを逆解析することで算出した光学特性値をモデル式より解析し、干渉効果の波長依存性を明らかにした。
3.分子動力学シミュレーションにより構造特性を計算し、干渉散乱理論に組み込んで散乱特性を計算した。粒子間の引力相互作用が散乱特性に強く影響を及ぼすことを明らかにした。
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 20H02076 - 高Oh液滴の固体面衝突直後に発生するsplashの相似則構築とメカニズム解明
科学研究費助成事業
01 Apr. 2020 - 31 Mar. 2023
渡部 正夫, 小林 一道, 藤井 宏之, 真田 俊之
本研究の目的は,「高Oh液滴の固体面衝突直後に発生するcorona splashとprompt splashの発生条件を明らかにし,二つのsplashの発生メカニズムを説明する理論モデルを構築すること」である.この目的を達成するために,本年度は以下の2項目について研究を行った.
1.固体表面に滴衝する高Oh液滴の観察:自由落下するシリコンオイルを用いて衝突実験を行い,高Oh液滴のsplash発生条件を探索した.高粘度液滴衝突ではあるOhを閾値としてsplashとreceding break-upの2種類の不安定性が観察されること, 閾値Oh数以上ではreceding break-upのみが観察されさらにOh数を大きくすると不安定性が観察されないこと,receding break-upはある衝突速度以上では観察されないことを明らかにした.
2.粗い表面に衝突する液滴の観察:低圧力環境下の高速液滴衝突 (50m/s程度) 実現を行い,固体表面粗さの効果を検討するために,減圧チャンバ内での粗い固体表面への高速液滴衝突を観察した.平滑表面および粗い固体表面においてsplashの発生閾値を検討した.低Oh液滴衝突においては,これまで観察されていたcorona splashとprompt splashに加えて衝突直後極短時間にのみ観察されるsplashが存在することが発見され,これまでに提案されたsplash発生閾値モデルは,粗い表面には適用できないことを明らかにした.
3.高速度カラー光干渉計による気液界面計測システムによる観察:固体表面に衝突する液滴の固体面衝突直前に,固体表面と液滴との間に形成される薄空気膜はsplash発生に大きな影響を与える.この薄空気膜厚さの空間分布の時間変化が,固体表面電位と液体の誘電率によって大きく変化することを明らかにした.
日本学術振興会, 基盤研究(B), 北海道大学, 20H02061 - 表面プラズモン共鳴観察によるアクティブマターのメカニズムの解明
科学研究費補助金(挑戦的研究(萌芽))
Apr. 2018 - Mar. 2020
渡部 正夫
日本学術振興会, Principal investigator, Competitive research funding - 高速射出液膜流れの固気液三相接触線近傍流れ場の不安定現象に及ぼす周囲気体効果
科学研究費補助金(基盤研究(B))
Apr. 2017 - Mar. 2020
渡部 正夫
日本学術振興会, Principal investigator, Competitive research funding - Determination of kinetic boundary conditions for gas-vapor binary mixture and its application
Grants-in-Aid for Scientific Research
01 Apr. 2016 - 31 Mar. 2019
Kobayashi Kazumichi, KON Misaki
The aim of this study is to determine the kinetic boundary conditions for vapor (condensable gas) - gas (non-condensable gas) binary mixture. We also apply the boundary conditions for multi phase flow, especially for the analysis of bubble collapse problem.
In the present study period, molecular dynamics method was used to construct the kinetic boundary conditions for vapor-gas mixture at equilibrium. We also solved the problem of the bubble collapse using the boundary conditions obtained from the molecular dynamics simulation. As a result, it was suggested that a thin layer composed of non-condensable gas is formed in the vicinity of the gas-liquid interface when the bubble collapses, and it was indicated that the condensation coefficient becomes extremely low due to the influence of this layer. It was also revealed that the internal temperature field when bubble collapses was affected by a small amount of non-condensable gas contained in the bubble.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (C), Hokkaido University, 16K06064 - Condensation effect on high-speed liquid-film flow instability at a liquid-droplet impact on a solid surface in a vaporous environment
Grants-in-Aid for Scientific Research
2014 - 2016
WATANABE MASAO
Droplet impacts on solid surface are key elements in technical applications, such as rapid spray cooling, ink-jet printing and semiconductor cleaning. Although the broad varieties of parameters that control splash formation after the droplet impact, are proposed, they are not thoroughly explored; hence, dynamics of the droplet after the impact are yet fully understood. After droplet impacts on solid surface, characteristic film flow is developed; then splash may be generated. In this study, we examine the effects of the temperature of surrounding gas, which is either condensable or non-condensable, on ethanol droplet impact. We found that splash can be suppressed with the increase of the surrounding gas temperature. We measured the splash threshold pressure for a splash to appear as a function of the temperature. The results show that the splash threshold pressure is a monotonically increasing function of the surrounding gas temperature.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, Principal investigator, Competitive research funding, 26289031 - Investigation of mass transport mechanism in fuel cel by a hierarchical multi-physics simulation concept
Grants-in-Aid for Scientific Research
01 Apr. 2011 - 31 Mar. 2015
OSHIMA Nobuyuki, WATANABE Masao, KURIHARA Eru, YAGUCHI Hisao
For multi-scale flow phenomena concerning to fuel cell performance, a hierarchical multi-physics simulation concept is investigated to couple between molecular dynamics, non- equilibrium thermodynamics and unsteady flow simulation. Validations and improvements of mathematical models and numerical methods are performed on the following problems; 1) unsteady coupling simulation of cell / stack level performance of fuel cell design, 2) validations of lattice Boltzmann method for gas-liquid interface simulation and water transport models in catalyst layer, and 3) gas-liquid mixed gas simulation with 6-site potential model for water molecule.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (B), Hokkaido University, 23360079 - Study of unsteady heat and mass transfer at the strong non-equilibrium interface ugin mean-field kinetic theory
Grants-in-Aid for Scientific Research
2014 - 2015
Watanabe Masao, KOBAYASHI KAZUMICHI, YAGUCHI HISAO, HIROYUKI FUJII
The aim of this study is to examine a kinetic boundary condition that depends on liquid temperature for the Boltzmann equation in a vapor-liquid two-phase system during unsteady net evaporation/condensation in a strong non-equilibrium status.We carried out numerical simulations of the unsteady heat and mass transfer in the vicinity of interface at the strong non-equilibrium status by using EV-DSMC method; then, we constructed the kinetic boundary condition that can prescribe the heat and mass transfer in the vicinity of the interface in the frame work of the macroscopic fluid mechanics. We proposed a novel model of the bubble dynamics with phase change taken into consideration. We also investigated the bubble dynamics with phase change.
Japan Society for the Promotion of Science, Grant-in-Aid for Challenging Exploratory Research, Hokkaido University, Principal investigator, Competitive research funding, 26630043 - Development of nonlinear nonequilibrium fluid mechanics through comprehensive integration of molecular dynamics of vapor-liquid interface and molecular gas dynamics
Grants-in-Aid for Scientific Research
01 Apr. 2011 - 31 Mar. 2014
YANO Takeru, AOKI Kazuo, TAKATA Shigeru, WATANABE Masao
The ultimate goal of this research is to break a new ground of nonlinear nonequilibrium fluid mechanics by a comprehensive integration of molecular dynamics at the vapor-liquid interface and molecular gas dynamics based on the theory of Boltzmann equation. To this end, we have performed several specific analyses: 1. General formulation of nonequilibrium unsteady vapor motions accompanied with evaporation or condensation at the interface; 2. Establishment of reciprocity among elemental relaxation and driven-flow problems for a rarefied gas; 3. Careful investigation of applicability of macroscopic fluid mechanics to some nano-scale flows.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Osaka University, 23246034 - Study of elementary process of novel cleaning method by investigation of surrounding condensable vapor effect on single droplet drag reduction
Grants-in-Aid for Scientific Research(基盤研究(B))
2010 - 2012
Masao WATANABE, 真田 俊之, 小林 一道, 矢口 久雄
In the cleaning processes of manufacturing semiconductor deVices, two-fluidspray cleaning technique is widely used. In this study, we fbcus our attention to the elementary process ofthis cleaning technique, i.e. a single droplet impact on a solid surface. We experimentally observe impact ofsingle droplet on a rigid solid surface. Especially we focus on the effects of surfaces tension, surfaceroughness and surrounding pressure. Decrease of the surrounding gas pressure makes droplets alwayscreate lamella even in the cases with low surface tension and rough surfaces
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 北海道大学, Principal investigator, Competitive research funding, 22360073 - Study on Transport phenomena at supercritical mixure interface by moelcular velocity distribution function and mean field kinetic theory
Grants-in-Aid for Scientific Research(挑戦的萌芽研究)
2011 - 2011
Masato WATANABE, 小林 一道, 矢口 久雄
Transport phenomena on vapor-liquid mixture interface is studied for the accurate prediction of fuel mixture concentration,which leads to the development of highly reliable liquid fuel rocket engine. Numerical simulations f()r vapor liquid twophase systems were perf()mled by using the mean field kinetic theory.The kinetic boundaiy condition(KBC)at theinterface was investigated. We also execute molecular dynamics simulations oftwo-component vapor-liquid equilibrium systemsofbinary system to investigate heat/mass transport phenomena on mixtUre interface.
Ministry of Education, Culture, Sports, Science and Technology, 挑戦的萌芽研究, 北海道大学, Principal investigator, Competitive research funding, 23656122 - Multiscale study on molecular transport process near nonequilibrium vapor-liquid interfaces governed by three physical laws
Grants-in-Aid for Scientific Research
2009 - 2011
FUJIKAWA Shigeo, YANO Takeru, WATANABE Masao, KOBAYASHI Kazumichi, YAGUCHI Hisao, PENG Guoyi
This research project has been performed to clarify molecular transport process at vapor-liquid interfaces in nonequilibrium states by multiscale methods. The results can be summarized as follows :(1) Determination of evaporation and condensation coefficients by shock tube and molecular gas dynamics,(2) Determination of evaporation coefficient by sound wave,(3) Formulation of kinetic boundary condition at curved vapor-liquid interface, and (4) Asymptotic analysis of unsteady kinetic boundary condition at arbitrarily-shaped vapor-liquid interface by molecular gas dynamics.
Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research (A), Hokkaido University, Coinvestigator not use grants, Competitive research funding, 21246031 - 革新的洗浄方法原理解明のための水蒸気・水混相噴流衝突速度における凝縮効果の解析
科学研究費補助金(挑戦的萌芽研究)
2009 - 2010
渡部 正夫, 小林 一道
本研究では,研究代表者らが提案した水蒸気と水を混合しノズルから噴射する革新的混相噴流洗浄方法の基本原理を解明することを目的としている.具体的には,水蒸気中の水液滴が固体表面上の水液膜に衝突することにより発生する衝突圧力に着目する.この衝突圧力は,液滴衝突速度に大きく左右されるため,衝突速度を正確に見積もる必要があり,液滴界面および固体表面での凝縮効果を高精度で解析することが必要である.従って,分子気体力学を用いることが必要不可欠である.本年度は,昨年度構築した気体分子力学と連続体数値流体力学を融合させた数値解析スキーム開発のための基礎モデルの評価を行った.球対称一次元座標系を用いて,Gaussian-BGK-Boltzmann方程式に従う多原子分子気体が,球形液滴に凝縮する過程の数値シミュレーションを行った.液滴周囲の圧力分布を観察することにより液滴に働く抗力を算出した.気液界面の境界条件を支配する蒸発・凝縮係数に液滴抗力は大きく依存し,蒸発・凝縮が発生することにより液滴抗力が低下することを確認した.さらに,より現実的な系を取り扱うために,気体中に分子の占める体積が無視できないような高密度の気体に対して有効である,Enskog-Vlasov方程式を用いることを試みた.Boltzmann方程式の直接解法であるDSMC法を拡張したParticle Scheme法を用いて,単純な系...
文部科学省, 挑戦的萌芽研究, 北海道大学, Principal investigator, Competitive research funding, 21656048 - Development of functional surface structure and lubrication ability in articular cartilage tissue under tribologycal stimulation
Grants-in-Aid for Scientific Research(基盤研究(B))
2008 - 2010
Yoshinori SAWAE, Masao WATANABE, Nobuo SAKAI
Process and mechanism in the functional adaptation of superficial zone tissue structure of articular cartilage to tribological stimulations was explored. A well established three dimensional culture system for isolated chondrocytes, chondrocyte-agarose construct, was employed as a regenerated cartilage model and mechanical stimulations, such as cyclic compression, shear and surface friction, were applied to the model to examine their effects on cell metabolisms and the subsequent development of functional tissue structure for joint lubrication.
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学, Coinvestigator not use grants, Competitive research funding, 20360078 - Modeling of Transport Phenomena and Physical Stimulus Response in Engineered Cartilage Tissue Development
Grants-in-Aid for Scientific Research(基盤研究(B))
2007 - 2009
Masao WATANABE, 坂井 伸朗, 真田 俊之, 澤江 義則, 坂井 伸朗, 真田 俊之
We visualized transport phenomena in developing engineered cartilage tissues. The promotion of mass transfer due to the existence of cells inside test pieces are observed. The cell metabolism increased the diffusion transport. Generated polymers that consist extra-cellular matrices, such as negatively charged keratan sulfate, restrict diffusion transport. We also clarified the effects of advection transport due to the compression on diffusion transport.
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学->北海道大学->九州大学->北海道大学, Principal investigator, Competitive research funding, 19360087 - Effects of tribological stimulation on chondrocyte metabolism and development of functional cartilage tissue structure for joint lubrication
Grants-in-Aid for Scientific Research(基盤研究(C))
2006 - 2007
Yoshinori SAWAE, 渡部 正夫
Articular cartilage is one of the unique and interesting soft tissues since it covers articulating surfaces of diarthrodial joints and plays an important role as "bearing" to achieve smooth joint movements. However, the detailed mechanism which governs the establishing process of the sophisticated tribological functions on the cartilage surface has not been clarified yet The purpose of this research project has been to investigate the developing process of functional cartilage tissue structure for the joint lubrication by the metabolic response of chondrocytes to the mechanical loadings exp...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 九州大学, Coinvestigator not use grants, Competitive research funding, 18560137 - Milli, Micro and Nano Fluidics in Air-Lift Operated Tank for Culture of Animal Cell
Grants-in-Aid for Scientific Research(基盤研究(B))
2005 - 2006
Masao WATANABE, 真田 俊之, 澤江 義則, 杉村 丈一
For the further improvement of bubble-driven airlift-operated tank for closed-system culture of animal cell, we studied both rising bubble behavior, and transport phenomena of cell and extra cellular matrix.It is highly required for the realization of the homogeneous bubbly flow that the most optimized bubble number density, i.e., bubble diameter and bubble mutual distance, should be determined. We observed the bubble motion in super purified water since the surfactant effects are essential for the bubble motion.It was found that the contact time of rising bubble with free surface was const...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学, Principal investigator, Competitive research funding, 17360082 - ヒト皮膚毛細管動静脈ループの血流動態と血管形状の非侵襲・高時空間解像度解析
科学研究費補助金(萌芽研究)
2005 - 2005
渡部 正夫, 真田 俊之, 澤江 義則, 古江 増隆
本研究の目的は,ヒト皮膚毛細管動静脈ループに注目し,血流動態と血管形状の非侵襲・高時空間解像度解析を行うシステムを開発することである.まず,ヒト爪郭皮膚毛細管動静脈ループを観測するために,計測システムを構築した.特に,被写体から対物レンズまでの距離を固定し,被写体のブレを抑えるために光学アタッチメントの開発を行い,実用に耐えうることを確認した.また,高速度カメラで被写体を撮影し,画像のブレを抑制するためにシャッタースピードを上げる必要があるために光源の高光度が要求されるが,光源は熱源となるために過度の光量は被写体の熱損傷を引き起こす.光源・レンズ・光学系の設計・開発を行い,照射面積を大幅に減じ効率の向上を図った結果,鮮明な画像取得と被写体の低侵襲観察の相反する要求を満足させることに成功した.さらに,フレキシブルアームスタンドによりカメラを固定することにより,光軸に空間自由度を与えることに成功し,ヒト皮膚毛細管動静脈ループに限定されない他の皮膚毛細血管,特に血管腫等の観察の臨床応用に適用可能であることを示した.得られた画像には,Matlabを用いて様々な画像処理を施すことにより画像強調を行い,生画像に比して格段の視認性を得られることを確認した.10μm程度の径を持つ細小動静脈管内を流れる赤血球,白血球および血漿の非定常挙動の観察に成功した.また,医療画像認識工学で用いられるレベ...
文部科学省, 萌芽研究, 九州大学, Principal investigator, Competitive research funding, 17656068 - Bio-Material Transport Pump Activated by Liquid Jet around Single Rising Bubble Chain
Grants-in-Aid for Scientific Research(基盤研究(B))
2003 - 2004
Masao WATANABE, 松下 大介, 古川 明徳
It was confirmed that a characteristic flow field existed in surroundings of the rising bubble chain which was row though it was generated from a single nozzle. The bubble chain was generated in the water pool with both the bubble diameter and bubble generation frequency accurately controlled, and the generation process of this characteristic flow field in the neighborhood of the bubble chain was observed. The lift force acting on bubbles in the bubble chain is larger than the one acting on a single bubble, due to the flow field formed by the leading bubbles. It is considered that the wake ...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学, Principal investigator, Competitive research funding, 15360096 - 数値流体力学とMR血流データとを用いた高精度血管セグメンテーション法の開発
科学研究費補助金(萌芽研究)
2003 - 2004
渡部 正夫
1.磁気共鳴位相コントラスト血管撮像法(MR-PCA)において,数値流体力学の手法を用いることにより,得られた血流流れ場を修正すると共に,より高精度の血管形状の認識・輪郭抽出を行うための手法を提唱し,高制度化をはかった。特に本手法は初期の血管セグメンテーションに精度が依存するために,より高精度化をはかるため,レベルセット法を用いた三次元医療イメージングの輪郭抽出において,閾値法に基づく手法を検討した.レベルセット法の中で適用例の多い再初期化法と測地的動的輪郭法とを組み合わせることにより,再初期法の堅牢性・収束性の良さと,測地的動的輪郭法の解曲面の平滑性とを併せ持つ手法を開発した.この手法のパラメータ強度を調査するために,MRデータのみならず,毛細血管データにも適用し複雑血管形状を抽出した.血管壁認識力の高い再初期化法と血管壁再構成力の高い測地的動的輪郭法との混合を単一のパラメータで制御することが可能であることを認識した.さらに,測地的動的輪郭法の特徴を生かすことにより,従来は画像幾何より求められていた血管の管径・曲率等の特徴値をレベルセット関数を用いて解析的に求める手法を提唱した.2.複雑な3次元血管内の血流をシュミレートするためには,単純な境界条件と並列化の容易さが要求される.そこで,血流流れソルバを従来の差分法から格子ボルツマン法へと改良するための検討を行った.特に境界条...
文部科学省, 萌芽研究, 九州大学, Principal investigator, Competitive research funding, 15656051 - RESEACH ON THE GENERATION MECHANISM OF BURNOUTNEAR THE FLOW OBSTRACTION IN BOILING TWO-PHASE FLOW WITHIN ANANNULAR CHANNEL
Grants-in-Aid for Scientific Research(基盤研究(B))
2002 - 2003
Tohru FUKANO, 渡部 正夫
In order to clarify the mechanism of burnout occurrence near the obstacle, which simulate spacers of BWR, flow phenomena was carefully observed' by using a high-speed video and time varying wall temperatures were measured at many axially different locations. The results are summarized as follows.1.In relation to the occurrence of burnout, we carefully observed two-phase flow phenomena. The generation of dry-out of liquid film, which acts as a trigger of generation of burnout, is caused by the dry-out of base film between two disturbance waves at the location upstream of the spacer. On the o...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学, Coinvestigator not use grants, Competitive research funding, 14350094 - 軟骨生体組織内マクロ輸送現象の流体力学モデルの構築
科学研究費補助金(萌芽研究)
2002 - 2002
渡部 正夫, 松下 大介
血管が存在しない軟骨組織を対象として,生体組織における組織レベルのマクロスケールなマクロな輸送現象輸送現象に関して研究を行った.軟骨組織内には血管細胞が欠如しているため,組織内の輸送現象は主に拡散・浸透によるものであると考えられる.本研究では分子量の異なる蛍光マーカーを培地に混入し,牛関節軟骨より切り出した軟骨微小組織切片を一定期間培養し,蛍光マーカーが拡散した軟骨組織の,連続凍結切片の蛍光顕微鏡像に画像処理を施し,蛍光マーカー空間分布を定量化することにより,細胞組織内への輸送現象を観察した.その結果,以下の知見を得た.1.軟骨組織内の物質輸送は,組織の幾何学的構造,生物理学的特徴の異方性により大きく影響を受ける.軟骨組織の加重方向に輸送されるマーカー量は,加重方向の直交方向に輸送されるマーカー量に卓越している.特に軟骨組織表層部よりのマーカーの浸入が顕著であることが観察された.2.分子量の異なるマーカーを用いることにより,拡散速度および拡散量に大きな違いが観察された.特に,分子量500kD程度のマーカーの場合には,組織内部への侵入がほとんど観察されなかった.3.分子量の等しいFITC-dextranとRITC-dextranをマーカーとして用い,12時間培養を行った結果,拡散様式に大きな違いが観察された.FITCは負に荷電され,RITCは中性であることが,電気泳動を用いて確...
文部科学省, 萌芽研究, 九州大学, Principal investigator, Competitive research funding, 14655073 - Development of the Cooling System for MPU of Mobile Personal Computer
Grants-in-Aid for Scientific Research(基盤研究(B))
2001 - 2002
Tohru FUKANO, 宮原 雅晴, 渡部 正夫
Mobile personal computers are developing quickly in miniaturization with high performance. With this direction heat generation from the MPU will become higher and higher. And in near future it is supposed to become twice and triple times of the present value. And therefore the high heat generation must be taken into consideration in thermal design of such mobile computers. Recent investigation shows that the heat can be distributed by use of a small size heat pipes. The accumulated heat within the case of the computer, however, must be eventually transferred out of the case by use of some k...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学, Coinvestigator not use grants, Competitive research funding, 13555047 - 気泡の体積変化を利用したマイクロポンプの作動原理に関する熱流体力学的研究
科学研究費補助金(奨励研究(A))
2000 - 2001
渡部 正夫
気泡運動を利用したマイクロポンプの作動原理を理解するためには,気泡運動により誘起される周囲流体挙動を解析することが必要である.特に,今年度は気泡運動が比較的単純な場合についてのみ検討することにより,基礎的データを取得することを目的とした.そのため,モノポールとダイポールがそれぞれ支配的な流れ場について考察を行なった.気泡運動として径方向運動(モノポール)が支配的な流れ場に関しては,より複雑な流れ場を形成し得る気泡群の挙動により誘起される周囲流体,特に形成される圧力場に関して考察した.多数の気泡が液体中のある領域内に高い密度で存在する気泡群の場の圧力の変動に対する挙動を,多重極展開法・摂動展開法に基づく数学モデルを構築し数値計算を行なった.気泡群の線形圧力応答を解析することにより,少数の気泡が存在すれば,連続体モデルにより予測される音響特性を生じることが確認された.また,離散モデルを用いて,気泡群周囲圧力を急激に上昇させることにより気泡群内の気泡を収縮させる,キャビテーション気泡群崩壊の単純モデルを提案した.並進運動(ダイポール)が支配的な流れ場を解析するためには,最も単純な場合であると考えられる同一直線上を上昇する気泡による流れ場解析を有限要素法による数値シミュレーションにより行なった.DSD/ST(deforming-spatial-domain/space-time)有限...
文部科学省, 奨励研究(A), 九州大学, Principal investigator, Competitive research funding, 12750143 - Mechanisms of Burnout Generation due to the Instability and the Transient Change of Boiling Two-Phase Flow near a Flow Obstacle simulating a Spacer of a BWR
Grants-in-Aid for Scientific Research(基盤研究(B))
2000 - 2001
Tohru FUKANO, 渡部 正夫
A cylindrical flow obstruction which simulates a spacer supporting nuclear fuel rods in BWR was installed in the vertical annular channel. Flow patterns, especially the generation of drypatch and burnout, were carefully observed by a high speed video camera. The time variations of temperature on the heating tube surface were simultaneously measured near the spacer at six axially different location under the experimental conditions of transiently changing flow caused by the sudden change in the heart flux, the inlet quality, the mass flow rate. The effect of flow instability on the generatio...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学, Coinvestigator not use grants, Competitive research funding, 12450076 - MRアンギオグラフィーにおける血流流れ場シミュレーションと血管セグメンテーションとのレベルセット法による統合
2001
Competitive research funding - RESEARCH ON THE GENERATION MECHANISM OF BURNOUT JUST UPSTREAM OF THE SPACER SUPPORTING BWR-NUCLEAR ROD BUNDLE
Grants-in-Aid for Scientific Research(基盤研究(B))
1998 - 1999
Tohru FUKANO, 渡部 正夫
A cylindrical flow obstruction which simulates a spacer supporting nuclear fuel rods in BWR was installed in the vertical annular channel. Flow patters, especially the generation of drypatch and burnout, were carefully observed by a high speed video camera. The time variations of temperature on the heating tube surface were simultaneously measured near the spacer at six axially different locations. The results are summarized as follows.(1) Large amplitude temperature change is caused by rapid increase in heat transfer through quite thin liquid film prior to the generation of drypatch which ...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 九州大学, Coinvestigator not use grants, Competitive research funding, 10450087 - 変形気泡の相互干渉を考慮に入れた気泡群の挙動に関する流体力学的研究
科学研究費補助金(奨励研究(A))
1997 - 1998
渡部 正夫
多数の気泡を含んだ液体(気泡群)の流体力学的挙動をモデル化するために気泡相互作用・気泡変形を考慮に入れたマクロモデルの基礎となる,ミクロ要素モデルを構築することを目的とした.今年度は特に静止流体中を上昇する気泡および気泡列の挙動および周囲液体へ及ぼす影響を解明するための,基礎実験および数値解析を行った.実験においては,気泡周りの流れ場を計測するために,様々なトレーサと光源を用いることにより得られた二次元流体画像に対して,昨年度購入したグラフィックワークステーション上で開発されたPIV法による流れ場計測用処理プログラムを用いて,静止流体中における単一上昇気泡および上昇気泡列まわりの流れ場に適用した.ステレオ画像を用いることにより気泡後流の発達過程と気泡の上昇過程との相互作用を観察し,気泡変形および放出渦の相互干渉に関して知見を得た.数値計算によるアプローチにおいては,DSD/ST有限要素法を用いることにより,気泡を含む軸対称二次元流れ場を解析するための計算コードを解析し,気泡形状の変形および境界の影響に関してして調査を行った.特に可視化実験の比較対照モデルとなる2気泡の運動に関して詳細な検討を行い,同一直線上を上昇する二気泡の運動に関して数値シミュレーションを行い,気泡変形が気泡相互作用に及ぼす影響を様々な表面張力係数を用いることにより解析を行い,また,界面活性剤の影響を計算コ...
文部科学省, 奨励研究(A), 九州大学, Principal investigator, Competitive research funding, 09750197 - THERMO-FLUID DYNAMIC RESEARCH ON THE CHARACTERISTICS OF HEAT REMOVAL FROM THE NUCLEAR FUEL RODS NEAR THE SPACER
Grants-in-Aid for Scientific Research(一般研究(B), 基盤研究(B))
1995 - 1996
Tohru FUKANO, 大田 治彦, 後藤 昭和, 渡部 正夫
The effects of the geometry of the spacer, which supports the nuclear rods, on the thermo-fluid phenomena near the spacer were investigated by using two different types of the spacers. One is the ring type and the other is the grid type spacers. The special attention was focused on (a) the mechanism to cause the drypatch dormation, (b) the frequency of the drypatch formation and (c) the temperature distribution near the down side of the spacer. The results are summarized as follows.(1) Even if there is a gap between the spacer and the heating tube surface, the coolant water stagnates in bet...
Ministry of Education, Culture, Sports, Science and Technology, 一般研究(B), 基盤研究(B), 九州大学, Coinvestigator not use grants, Competitive research funding, 07455086 - 気泡群の音響特性の直接シミュレーション
Competitive research funding - 気泡運動の数値解析
Competitive research funding - Dynamic Simulation of the Acoustic Characteristics of Bubble Clouds
Competitive research funding - Thermo-Fluid Mechanical Study of the Thermoacoustic Devices
Competitive research funding - Numerical Simulation of Bubble Motions
Competitive research funding