Researcher Profile and Settings

Affiliation

• Faculty of Engineering　Mechanical and Aerospace Engineering　Thermal and Fluid Systems

Job Title

• Associate Professor

URL

https://tfp.eng.hokudai.ac.jp

J-Global ID

• 200901052576073672

Research Interests

• Molecular dynamics   Kinetic theory of gases   Droplet   Bubble   Interface   分子流体力学   Fluid Mechanics   

Research Areas

• Manufacturing technology (mechanical, electrical/electronic, chemical engineering) / Fluid engineering

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

Academic & Professional Experience

• 2013/04 - Today Hokkaido University, Faculty of Engineering Associate Professor
• 2015/04 - 2015/09 Nagoya University Graduate School of Engineering Part-time lecturer
• 2010/04 - 2013/03 Hokkaido University, Faculty of Engineering Assistant Professor
• 2007/04 - 2010/03 Osaka Prefecture University Assistant Professor
• 2006/04 - 2007/03 Hokkaido University, Graduate school of Engineering JPSP Fellowship Researcher

Education

• 2004/04 - 2007/03  Hokkaido University  Division of Mechanical Science
• 2002/04 - 2004/03  Hokkaido University  Graduate school of Engineering
• 1998/04 - 2002/03  Hokkaido University  School of Engineering  Department of Mechanical Engineering

Association Memberships

• The Heat Transfer Society of Japan   THE JAPANESE SOCIETY FOR MULTIPHASE FLOW   The Japan society of Thermophsical Properties   THE JAPAN SOCIETY OF FLUID MECHANICS   THE PHYSICAL SOCIETY OF JAPAN   THE JAPAN SOCIETY OF MECHANICAL ENGINEERS   

Research Activities

Published Papers

• 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) 082021 - 082021 1070-6631 2023/08/01 [Refereed][Not invited]
   

  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 1350-4495 2023/08
• 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 0735-1933 2023/03 [Refereed][Not invited]
  
• 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 1359-4311 2022/07 [Refereed][Not invited]
  
• 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 1070-6631 2022/06 [Refereed][Not invited]
   

  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.
• 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 2213-5979 2022/06 [Refereed][Not invited]
  
• 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 0017-9310 2022/06/01 [Refereed][Not invited]
  
• 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 2022/01/31 [Refereed][Not invited]
  
• 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 2022/01/24 [Refereed][Not invited]
   

  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 1070-6631 2021/12/22 [Refereed][Not invited]
  
• 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 2021/03/16 [Refereed]
   

  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 0021-9991 2020/09 [Refereed][Not invited]
  
• 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 2020/07/10 [Refereed][Not invited]
  
• Evaporation coefficient and condensation coefficient of vapor under high gas pressure conditions

  Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe

  Scientific Reports 10 8143  2020/05 [Refereed][Not invited]
  
• Levitation mechanism of impacting nanodroplet on heated wall

  Hirofumi Tabe, Kazumichi Kobayashi, Hisao Yaguchi, Hiroyuki Fujii, Masao Watanabe

  International Journal of Thermal Science 150 106203 - 106203 1290-0729 2020/04 [Refereed][Not invited]
  
• 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) 2020/01/15 [Refereed][Not invited]
  
• 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 93  2020 [Refereed][Not invited]
  
• Influence of a small amount of non-condensable 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) 063603  2019/06 [Refereed][Not invited]
  
• 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 0947-7411 2019/04 [Refereed][Not invited]
  
• Molecular gas dynamics analysis on condensation coefficient of vapour during gas-vapour bubble collapse

  Kazumichi Kazumichi Kobayashi, Takahiro Nagayama, Masao Watanabe, Hiroyuki Fujii, Misaki Kon

  Journal of Fluid Mechanics 856 1045 - 1063 2018/12 [Refereed][Not invited]
  
• Pressure generated at the instant of impact between a liquid droplet and solid surface

  Yuki Tatekura, Masao Watanabe, Kazumichi Kobayashi, Toshiyuki Sanada

  Royal Society Open Science 5  - 181101 2018/12 [Refereed][Not invited]
  
• 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 Watanabea

  Journal of Computational Physics 2018/07 [Refereed][Not invited]
  
• 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 1878-5204 2018/04/01 [Refereed][Not invited]
   

  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 2018 [Refereed][Invited]
  
• 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 0997-7546 2017/07 [Refereed][Invited]
   

  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.
• 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) 2040-7939 2017/05 [Refereed][Not invited]
   

  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.
• 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 1613-4982 2017/03 [Refereed][Not invited]
   

  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 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 0947-7411 2016/09 [Refereed][Not invited]
   

  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 0017-9310 2016/08 [Refereed][Not invited]
   

  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.
• 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)  - 032002 1070-6631 2016/03 [Refereed][Not invited]
   

  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.
• Estimation of evaporation mass flux at vapor-liquid interface during nonequilibrium evaporation/condensation

  Misaki Kon, Kazuichi Kobayashi, Kiyofumi Sasaki, Masao Watanabe

  Japanese Journal of Multiphse flow 日本混相流学会 29 (5) 493 - 500 0914-2843 2016/03 [Refereed][Invited]
   

  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.
• Study on Pressure Wave Propagation in a Liquid Containing Spherical Bubbles in a Rectangular Duct

  Junya Kawahara, Masao Watanabe, Kazumichi Kobayashi

  Journal of Physics: Conference Series 656 012023 - 012023 1742-6588 2015/12/03 [Refereed][Not invited]
   

  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.
• 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

  Journal of Physics: Conference Series 656 012021 - 012021 1742-6588 2015/12/03 [Refereed][Not invited]
   

  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.
• How do bubbles reduce the speed of sound in a bubbly liquid in a duct?

  Kazumichi KobayashiJunya Kawahara, Masao Watanabe, Kazumichi Kobayashi

  Mechanical Engineering Letters 1 115-00464 - 15-00464 2015/12 [Refereed][Not invited]
  
• Liquid film flow generated by high-speed droplet impact in low-pressure enviroment

  Masaya Kato, Masao Watanabe, Kazumichi Kobayashi, Toshiyuki Sanada

  Japanese Journal of Multiphase Flow 28 (5) 531 - 536 2015/03 [Refereed][Invited]
  
• Numerical study of light propagation in agricultural products for non-destructive assessment of food quality 1

  Kiyohito Hattori, Hiroyuki Fujii, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe

  Progress in Biomedical Optics and Imaging - Proceedings of SPIE 9792 1605-7422 2015 [Refereed][Not invited]
   

  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.
• 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 2162-8769 2015 [Refereed][Not invited]
   

  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.
• Method of determining kinetic boundary conditions in net evaporation/condensation

  Misaki Kon, Kazumichi Kobayashi, Masao Watanabe

  PHYSICS OF FLUIDS 26 (7)  - 072003 1070-6631 2014/07 [Refereed][Not invited]
   

  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.
• Evaporation and Condensation Coefficients of Methanol at Room Temperature, and Consideration of Kinetic Boundary Condition

  Kazumichi Kobayashi, Shingo Mouri, Yusuke Watanabe, Masao Watanabe, Shigeo Fujikawa

  Netsu Bussei JAPAN SOCIETY OF THERMOPHYSICAL PROPERTIES 27 (1) 9 - 14 0913-946X 2013/01 [Refereed][Not invited]
   

  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.
• 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 日本流体力学会 31 (6) 487 - 490 0286-3154 2012/12/25 [Not refereed][Not invited]
  
• Thin Film Removal by Steam and Water Mixed Spray (Removal Characteristic of Deposited Aluminum Film and Effects of Surface Temperature Change)

  Toshiyuki Sanada, Kentaro Hashimoto, Shouji Hayashida, Kazumichi Kobayashi, Masao Watanabe

  Konsoryu THE JAPANESE SOCIETY FOR MULTIPHASE FLOW 26 (2) 172 - 177 0914-2843 2012 [Refereed][Not invited]
   

  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)

  Yasutaka Sakurai, Kazumichi Kobayashi, Toshihide Fujikawa, Toshiyuki Sanada, Masao Watanabe

  Konsoryu 26 (2) 164 - 171 0914-2843 2012 [Refereed][Not invited]
  
• High-Speed Droplet Impact as an Elementary Process of Physical Cleaning

  Toshihide Fujikawa, Yuuki Tatekura, Kazumichi Kobayashi, Toshiyuki Sanada, Atsushi Hayashida, Masao Watanabe

  ECS Transactions 41 (5) 67 - 74 1938-5862 2011/10/04 [Refereed][Not invited]
   

  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 plate 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 also spreads obliquely upward. The obliquely upward flow field may also contribute in advecting removed particles or stripped resists away from the original place.
• Shock wave-bubble interaction near soft and rigid boundaries during lithotripsy: numerical analysis by the improved ghost fluid method

  Kazumichi Kobayashi, Tetsuya Kodama, Hiroyuki Takahira

  PHYSICS IN MEDICINE AND BIOLOGY 56 (19) 6421 - 6440 0031-9155 2011/10 [Refereed][Not invited]
   

  In the case of extracorporeal shock wave lithotripsy (ESWL), a shock wave-bubble interaction inevitably occurs near the focusing point of stones, resulting in stone fragmentation and subsequent tissue damage. Because shock wave-bubble interactions are high-speed phenomena occurring in tissue consisting of various media with different acoustic impedance values, numerical analysis is an effective method for elucidating the mechanism of these interactions. However, the mechanism has not been examined in detail because, at present, numerical simulations capable of incorporating the acoustic impedance of various tissues do not exist. Here, we show that the improved ghost fluid method (IGFM) can treat shock wave-bubble interactions in various media. Nonspherical bubble collapse near a rigid or soft tissue boundary (stone, liver, gelatin and fat) was analyzed. The reflection wave of an incident shock wave at a tissue boundary was the primary cause for the acceleration or deceleration of bubble collapse. The impulse that was obtained from the temporal evolution of pressure created by the bubble collapse increased the downward velocity of the boundary and caused subsequent boundary deformation. Results of this study showed that the IGFM is a useful method for analyzing the shock wave-bubble interaction near various tissues with different acoustic impedance.
• Behavior of Phospholipid Layer-Coated Microbubbles under Pressure Change

  Yuki Tanaka, Kazumichi Kobayashi, Hiroyuki Takahira

  Japanese Journal of Multiphase Flow 日本混相流学会 24 (5) 559 - 566 0914-2843 2011/03 [Refereed][Invited]
  
• Application of Multigrid Ghost Fluid Method to the Interaction of ShockWaves with Bubbles in Liquids

  Kazumichi Kobayashi, Yoshinori Jinbo, Hiroyuki Takahira

  Transactions of the Japan Society of Mechanical Engineers, Series B 77 (773) 20 - 32 1884-8346 2011/01 [Refereed][Not invited]
  
• Boundary element analysis of bubble dynamics under a floating body (2nd report, approximation method with spherical bubble model)

  Yoshinori Jinbo, Hiroyuki Takahira, Kazumichi Kobayashi, Akihiro Yasuda

  Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 76 (762) 230 - 238 0387-5016 2010 [Refereed][Not invited]
   

  A fast simulation method is proposed for underwater explosion. In the method, the motion of a bubble generated by the underwater explosion is modeled with a point source and a doublet the source and doublet represent the radial motion and translational of the bubble, respectively. The bubble motions are solved coupling with the motions of free surface and a floating body by using the boundary element method (BEM). The growth and collapse of a bubble under a floating body is simulated with the present method. It is shown that the present results are in qualitative agreement with those obtained from the BEM without the bubble model in which the interfacial motion of a bubble is solved directly with the BEM. The present simulation is found to be about six times faster than the BEM simulation without the bubble model.
• Boundary element analysis of bubble dynamics under a floating body (1st report, numerical simulation using the three-dimensional boundary element method with linear elements)

  Yoshinori Jinbo, Hiroyuki Takahira, Kazumichi Kobayashi, Akihiro Yasuda

  Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 76 (762) 219 - 229 0387-5016 2010 [Refereed][Not invited]
   

  The growth and collapse of a bubble under a floating body are simulated by using the boundary element method with linear elements to predict the damage of ship bodies induced by underwater explosion. The three-dimensional deformation of the bubble, the translation and rotation of the floating body, and the motion of water surface are taken into account in the simulation. It is shown that the bubble deforms three-dimensionally, and the liquid jet threads the bubble due to the interactions among the bubble, the floating body, and the water surface the directions of the bubble translation and the liquid jet depend on the initial location of the bubble. The Kelvin impulse is found to be useful in evaluating the translational motion of the bubble. Also, the horizontal translational motion of the bubble is much dependent on the rotational motion of a floating body when the moment of inertia of the floating body is small, the largest horizontal translation is realized between the axis of flotation and the edge of the floating body. It is also shown that there exists an initial horizontal bubble location where the moment of force acting on the floating body has the maximum value.
• Direct numerical simulations of interaction of strong shock waves with nonspherical gas bubbles near glass boundaries in mercury

  Hiroyuki Takahira, Kazumichi Kobayashi, Takahi Matsuno

  International Journal of Emerging Multidisciplinary Fluid Sciences 1 (2) 85 - 99 1756-8315 2009/06/01 [Refereed][Not invited]
   

  The present study is concerned with the material damage of the liquid-mercury target systems induced by bubble collapse. The interaction of an incident strong shock wave with an initially spherical bubble near a glass wall in mercury is simulated using an improved Ghost Fluid Method (GFM), in which Riemann solutions are utilized to correct the values at boundary nodes. The mercury and glass are evaluated by using the equation of state for stiffened gas. The axi-symmetric motions of three phases for air, mercury, and glass are solved directly coupling the GFM with the level set method. The interaction of the shock wave with the bubble leads to the bubble deformation and the formation of liquid-jet during the collapse. The strong shock waves are generated in the mercury not only when the bubble rebounds but also when the liquid-jet impacts downstream surface of the bubble. It is shown that the impact of the shock waves on the glass wall leads to the formation of depression of the glass surface the toroidal bubble formed after the impact of liquid-jet penetrates into the depression. The present results for the axi-symmetric bubble collapse are compared with those for the two-dimensional cylindrical bubble collapse. The stronger shock waves are generated when the axi-symmetric bubble collapses, which results in the higher impulsive pressure at the glass wall and the deeper depression of the glass surface.
• Condensation coefficient of water in a weak condensation state

  Kazumichi Kobayashi, Shunsuke Watanabe, Daigo Yamano, Takeru Yano, Shigeo Fujikawa

  FLUID DYNAMICS RESEARCH 40 (7-8) 585 - 596 0169-5983 2008/07 [Refereed][Not invited]
   

  The condensation coefficient of water at a vapor-liquid interface is determined by combining shock tube experiments and numerical simulations of the Gaussian-BGK Boltzmann equation. The time evolution in thickness of a liquid film, which is formed on the shock tube endwall behind the shock wave reflected at the endwall, is measured with an optical interferometer consisting of the physical beam and the reference one. The reference beam is utilized to eliminate systematic noises from the physical beam. The growth rate of the film is evaluated from the measured time evolution and it is incorporated into the kinetic boundary condition for the Boltzmann equation. From a numerical simulation using the boundary condition, the condensation coefficient of water is uniquely deduced. The results show that, in a condition of weak condensation near a vapor-liquid equilibrium state, the condensation coefficient of water is almost equal to the evaporation coefficient estimated by molecular dynamics simulations near a vapor-liquid equilibrium state and it decreases as the system becomes a nonequilibrium state. The condensation coefficient of water is nearly identical with that of methanol [Mikami, S., Kobayashi, K., Ota, T., Fujikawa, S., Yano, T., Ichijo, M., 2006. Molecular gas dynamics approaches to interfacial phenomena accompanied with condensation. Exp. Therm. Fluid Sci. 30, 795-800]. (c) 2008 The Japan Society of Fluid Mechanics and Elsevier B.V. All rights reserved.
• Molecular gas dynamics approaches to interfacial phenomena accompanied with condensation

  S. Mikami, K. Kobayashi, T. Ota, S. Fujikawa, T. Yano, M. Ichijo

  EXPERIMENTAL THERMAL AND FLUID SCIENCE 30 (8) 795 - 800 0894-1777 2006/08 [Refereed][Not invited]
   

  This paper deals with the condensation coefficient of methanol, which is evaluated from a condensation rate at the vapor-liquid interface. Film condensation is induced on the endwall of a vapor-filled shock tube, when a shock wave is reflected at the endwall and the vapor becomes supersaturated there. The liquid film grows with the lapse of time. The evolution in time of the liquid film thickness is measured by an optical interferometer with a high accuracy, and thereby the net condensation mass flux at the interface is obtained. The mass flux is incorporated into the kinetic boundary condition (KBC) at the interface for the Gaussian-BGK Boltzmann equation. Such a treatment of the boundary condition makes it possible to formally eliminate the evaporation and condensation coefficients in KBC and to obtain the unique numerical solution of the vapor-liquid system. In this way, the instantaneous condensation coefficient is accurately evaluated from the conformity with experiment and numerical solution. It is found that the values of condensation coefficient are, near vapor-liquid equilibrium states, close to those evaluated by molecular dynamics simulations. (C) 2006 Published by Elsevier Inc.
• Molecular gas dynamics of condensation processes of methanol vapor behind a reflected shock wave in a shock tube

  Takeru Yano, Kazumichi Kobayashi, Shigeo Fujikawa

  Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B 71 (702) 428 - 435 0387-5016 2005 [Refereed][Not invited]
   

  Film condensation phenomenon of methanol vapor at the endwall of a shock tube behind a reflected shock wave is studied by combining a shock tube experiment with a numerical analysis based on molecular gas dynamics. The present method of analysis utilizes the Gaussian-BGK Boltzmann equation, which is applicable to a strong condensation of polyatomic gases, and thereby some restrictions included in our previous method of analysis are removed. The result shows that the condensation cofficient is nearly unity when the ratio of the vapor pressure to the saturated vapor pressure at the interface is close to unity, and it decreases with the increase of the pressure ratio. Furthermore, the relations between the vapor condition and the condensation coefficient are extended to the second order so that it may contain the effect of moderately strong condensation and that of polyatomic molecules.
• Molecular gas dynamics applied to phase change processes at a vapor-liquid interface: shock-tube experiment and MGD computation for methanol

  S Fujikawa, T Yano, K Kobayashi, K Iwanami, M Ichijo

  EXPERIMENTS IN FLUIDS 37 (1) 80 - 86 0723-4864 2004/07 [Refereed][Not invited]
   

  This paper deals with a molecular gas-dynamics method applied to the accurate determination of the condensation coefficient of methanol vapor. The method consisted of an experiment using a shock tube and computations using a molecular gas-dynamics equation. The experiments were performed in such situations where the shift from a vapor-liquid equilibrium state to a nonequilibrium one is realized by a shock wave in a scale of molecular mean free time of vapor molecules. The temporal evolution in thickness of a liquid film formed on the shock-tube endwall behind a reflected shock wave is measured by an optical interferometer. By comparing the measured liquid-film thickness with numerical solutions for a polyatomic version of the Gaussian-BGK model of the Boltzmann equation, the condensation coefficient of methanol vapor is accurately determined in vapor-liquid nonequilibrium states. As a result, it is clear that the condensation coefficient is just unity very near to an equilibrium state, but is smaller far from the equilibrium state.

Books etc

• Influence of condensation coefficient on spherical bubble collapse with evaporation and condensation

  S. Morikawa, Y. Tatekura, K. Kobayashi, H. Fujii, M. Watanabe, K. Sasaki (Joint work)
  Japanese Society of Fluid Mechanics，NAGARE 2017/05 105-108 

  ながれ NAGARE 36
• Liquid temperature dependence of kinetic boundary condition at vapor–liquid interface

  Misaki Kon, Kazumichi Kobayashi, Masao Watanabe (Joint work)
  Advanced in Engineering 2017/03 

  https://advanceseng.com/mechanical-engineering/liquid-temperature-dependence-kinetic-boundary-condition-vapor-liquid-interface/
• Laboratory of Fluid Dynamics, Division of Mechanical and Space Engineering, Hokkaido University

  Masao Watanabe, Kazumichi Kobayashi, Hiroyuki Fujii (Joint work)
  Japanese Journal of Multiphase Flow 2016/12
• Mass, Momentum, and Energy transfer at vapor-liquid interface Chapter 5 Shock Tube Experiment of Evaporation and Condensation

  Kazumichi Kobayashi, Shigeo Fujikawa (Joint work)
  Japanese Society of Fluid Mechanics，NAGARE 2014/12 543-548 

  ながれ Nagare 33
• Report of JSMF Symposium on Multiphase Flow 2014

  Yuichi Murai, Kazumichi Kobayashi 
  混相流 Vol.28 No.4 日本混相流学会 2014/12 4
• Mass, Momentum, and Energy transfer at vapor-liquid interface Chapter 4 Application of Molecular Gas Dynamics to Evaporation and Condensation

  Kazumichi Kobayashi, Shigeo Fujikawa (Joint work)
  Japanese Society of Fluid Mechanics，NAGARE 2014/10 453-459 

  ながれ NAGARE 33
• 気液界面ダイナミクスのマルチスケール解析

  小林一道 
  えんじにあRing 北海道大学工学研究院・工学院 広報誌 2013/10 1 

  https://www.eng.hokudai.ac.jp/engineering/2013-10/index.html
• 相互作用を考慮した球形気泡離散モデルの解析（気泡流の音響特性）

  川原潤也, 小林一道, 渡部正夫 
  京都大学数理解析研究所講究録 2013
• Nonlinear Resonant Gas Oscillation with Evaporation and Condensation

  Masashi Inaba, Takeru Yano, Kazumichi Kobayashi, Masao Watanabe (Joint work)
  Japanese Society of Fluid Mechanics，NAGARE 2012/12 487-490 

  ながれ NAGARE 31
• 流体物理洗浄の概要と水蒸気二流体ジェットでの適用例

  真田俊之, 小林一道, 林田充司 (Joint work)
  産業洗浄 2012 14-19
• 気泡力学へのGhost Fluid法の適用

  高比良裕之, 小林一道 
  日本機械学会 流体工学部門 ニューズレター「流れ」9月号 2009 

  http://www.jsme-fed.org/newsletters/2009_9/no5.html#ctop
• Handbook of Interferometers: Research, Technology and Application

  Nova Science Publishers 2009 (ISBN: 9781607410508)

Conference Activities & Talks

• Mean-field kinetic theory analysis of vapor condensation induced by fast-moving liquid film  [Not invited]

  Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe

  AJK-FED 2023  2023/07
• Condensation Induced by Rapidly Moving Liquid Film Surrounded by Vapor and Non-condensable Gas  [Not invited]

  Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe

  32nd International Symposium on Rarefied Gas Dynamics  2022/07
• Mean-Field Kinetic Theory Analysis of Evaporation Coefficient and Condensation Coefficient of Vapor Molecules in the Presence of NonCondensable Gas under Non-Equilibrium Conditions  [Not invited]

  Kotaro Ohashi, Kazumichi Kobayashi, Hiroyuki Fujii, Masao Watanabe

  Pre-RGD32 Online Workshop on Recent Hot Topics in Rarefied Gas Dynamics  2021/07
• Numerical simulation of vapor bubble collapse with a small amount of non-condensable gas based on molecular gas dynamics  [Invited]

  Kazumichi Kobayashi

  Japan-Korea CFD Workshop  2019/11
• Surrounding gas-independent splash at high-velocity drop impact with a projected smooth solid surface  [Not invited]

  M. Watanabe, T. Ashida, K. Kobayashi, H. Fujii, T. Sanada

  The 72nd Annual Meeting of the American Physical Society’s Division of Fluid Dynamics  2019/11
• Molecular Dynamics Study on Influence of Liquid-solid Intermolecular Force on Levitating Mechanism of Impacting Nanodroplet on Heated Wall  [Not invited]

  H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe

  Surface Wettability Effects on Phase Change Phenomena(SWEP)  2019/06
• Molecular Gas Dynamics Analysis of Vapor-Gas Flow inside Collapsing Bubble  [Not invited]

  K. Yamamot, K. Kobayashi, H. Fujii, M. Watanabe, M. Kon, H. Takahira

  31th International Symposium on Rarefied Gas Dynamics (RGD31)  2018/07
• Influence of Surface Roughness of High Temperature Wall on Levitation of Impacting Droplet Based on Molecular Dynamics Simulation  [Not invited]

  H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe

  Surface Wettability Effects on Phase Change Phenomena(SWEP)  2018/05 

  SWEP BOOK of Abstract, p. 27
• Molecular Dynamics Study of Droplet Impact on High-Temperature Wall  [Not invited]

  H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe

  The 7th East Asia Mechanical and Aerospace Engineering Workshop  2017/11 

  1 page
• Numerical Investigation of Light and Pressure Propagation in Biological Tissue for Model-Based Photoacoustic Tomography  [Not invited]

  K. Tabayashi, H. Fujii, K. Kobayashi, M. Watanabe

  The Ninth JSME-KSME Thermal and Fluids Engineering Conference  2017/10 

  TFEC9-1526, 4 pages
• Numerical and Experimental Analysis of Droplet Impact in Vapor Environment  [Not invited]

  S. Sawai, T. Isono, H. Fujii, K. Kobayashi, M. Watanabe, T. Sanada

  The Ninth JSME-KSME Thermal and Fluids Engineering Conference  2017/10 

  TFEC9-1491, 5 pages
• Does Chemical Properties of Solid Surface Cause Liquid Film Flow Instability at Droplet Impact?  [Not invited]

  S. Tanimoto, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada

  The Ninth JSME-KSME Thermal and Fluids Engineering Conference  2017/10 

  TFEC9-­1334, 4 pages
• Observation of Splash Generated Immediately After the Impact of a High-Speed Droplet in Reduced-Pressure  [Not invited]

  T. Ashida, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada

  The Ninth JSME-KSME Thermal and Fluids Engineering Conference  2017/10 

  TFEC9-­1485, 4 pages
• Micro-Droplets Generation Induced by Interactions Between Focused Ultrasound and a Liquid Surface  [Not invited]

  K. Seko, K. Kobayashi, H. Fujii, M. Watanabe

  The Ninth JSME-KSME Thermal and Fluids Engineering Conference  2017/10 

  TFEC9-1173, 3 pages
• Molecular Dynamics Simulation of the Role of the Wettability in the Droplet Impact on a High-Temperature Wall  [Not invited]

  H. Tabe, K. Kobayashi, H. Yaguchi, H. Fujii, M. Watanabe

  The Ninth JSME-KSME Thermal and Fluids Engineering Conference  2017/10 

  TFEC9-1492, 4 pages
• Molecular Gas Dynamics Analysis of the Collapse of Microbubble Accompanied with Heat and Mass Transfer at Gas-Liquid Interface  [Invited]

  Kazumichi Kobayashi

  JSME Annual meeting  2017/09 

  【招待講演】
• 蒸気雰囲気中の液滴衝突に関する実験・分子流体力学解析  [Invited]

  Kazumichi Kobayashi

  Annual meeting of JSMF  2017/08 

  【招待講演】
• Numerical simulation of spherical vapor-gas bubble collapse  [Invited]

  Kazumichi Kobayashi, Misaki Kon, Takahiro Nagayama, Hiroyuki Fujii, Masao Watanabe, Hiroyuki Takahirav

  Japan-U.S. Seminar on Two-Phase Flow Dynamics  2017/06 

  【招待講演】
• Numerical simulation of pressure generated at the liquid droplet impact on a solid surface  [Not invited]

  Y. Tatekura, M. Watanabe, K. Kobayashi, T. Sanada

  The 3rd International Conference on Numerical Methods in Multiphase Flows  2017/06 

  B62, 2 pages
• Quantitative Method to Determine the Optical Properties of Melons by the Photon Diffusion Equation  [Not invited]

  K. Hattori, H. Fujii, G. Nishimura, K. Kobayashi, M. Watanabe

  The 5th Asian NIR Symposium  2016/11
• Optical properties of melons determined by an analysis based on the photon diffusion equation  [Not invited]

  K. Hattori, H. Fujii, G. Nishimura, K. Kobayashi, M. Watanabe

  1st Food Chemistry Conference  2016/10
• Nanoscale Thermal Fluid Dynamic at Vapor-Liquid Interface  [Invited]

  Kazumichi Kobayashi

  JSME Annual meeting  2016/09  九州大学伊都キャンパス  JSME
   

  【招待講演】
• Molecular simulation of evaporation mass flux during net evaporation/condensation  [Not invited]

  Misaki Kon, Kobayashi Kobayashi, Masao Watanabe

  The 30th International Symposium on Rarefied Gas Dynamics  2016/07  University of Victoria Victoria BC Canada 

  AIP Conf. Proc., Vol. 1786, 110001 (2016)
• Molecular dynamics simulation on kinetic boundary conditions of gas-vapor binary mixture  [Not invited]

  Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe

  The 30th International Symposium on Rarefied Gas Dynamics  2016/07  University of Victoria Victoria BC Canada 

  AIP Conf. Proc., 1786, 110002, (2016)
• Effects of surrounding gas temerature on ethanol droplet impact on solid surface  [Not invited]

  T. Isono, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada

  9th International conference on multiphase flow (ICMF2016)  2016/05
• Observation of non-sperical droplet imacts with velocities of O(10 m/s)  [Not invited]

  Y. Kataoka, Y. Hori, M. Watanabe, K. Kobayashi, H. Fujii, T. Sanada

  9th International conference on multiphase flow (ICMF2016)  2016/05
• Numerical analysis of bubble dynamics with vapor-liquid boundary conditions derived from molecular gas dynamics  [Not invited]

  S. Morikawa, J. Jinbo, Y. Tatekura, K. Kobayashi, M. Watanabe, H. Fujii, K. Sasaki

  9th International conference on multiphase flow (ICMF2016)  2016/05
• Numerical simulation of vapor-gas bubble dynamics based on molecular gas dynamics  [Not invited]

  T. Nagayama, M. Kon, K. Kobayashi, M. Watanabe, H. Fujii, H. Takahira

  9th International conference on multiphase flow (ICMF2016)  2016/05
• Molecular Dynamics Simulation on Kinetic Boundary Conditions of Gas-Vapor Binary Mixture  [Not invited]

  Kazumichi Kobayashi, Kiyofumi Sasaki, Misaki Kon, Hiroyuki Fujii, Masao Watanabe

  30TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS (RGD 30)  2016  AMER INST PHYSICS
   

  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.
• Microscopic Investigation of Boundary Condition at Vapor-liquid Interface during Unsteady Evaporation and Condensation  [Not invited]

  Misaki Kon, Kobayashi Kobayashi, Masao Watanabe

  2nd European conference on non-equilibrium gas flow  2015/12  Eindhoven, the Netherlands 

  Proceedings of 2nd European conference on non-equilibrium gas flow, No. 50, 1 page.
• Numerical simulation of bubble collapse and the transfer of vapor and noncondensable gas through the bubble interface using the ghost fluid method  [Not invited]

  Y Jinbo, K Kobayashi, M Watanabe, H Takahira

  Journal of Physics: Conference Series  2015/12  IOP Publishing
   

  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.
• Numerical simulation of bubble collapse and tranfer of vapor and noncondensable gas through the bubble interface using the ghost fluid method  [Not invited]

  Y. Jinbo, K. Kobayashi, M. Watanabe, H. Takahira

  9th International symposium on cavitation (CAV2015)  2015/12
• Study on Pressure Wave Propagation in a Liquid Containing Spherical Bubbles in a Rectangular Duct  [Not invited]

  J. Kawahara, M. Watanabe, K. Kobayashi

  9th International symposium on cavitation (CAV2015)  2015/12
• Numerical study of Light Propagation in Agricultural Products for Non-destructive Assessment of Food Quality  [Not invited]

  K. Hattori, H. Fujii, Y. Tatekura, K. Kobayashi, M. Watanabe

  Biophotonics Japan  2015/10
• Numerical simulation of compressible two-phase flows in high-speed impingement of a hollow droplet on a solid wall  [Invited]

  Y. Jinbo, K. Kobayashi, M. Watanabe, T. Sanada

  EMN Meeting on Droplets  2015/05 

  【Invited】Total 1 page
• Numerical study of light propagation in agricultural products for non-destructive assessment of food quality  [Not invited]

  Kiyohito Hattori, Hiroyuki Fujii, Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe

  BIOPHOTONICS JAPAN 2015  2015  SPIE-INT SOC OPTICAL ENGINEERING
   

  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.
• Molecular dynamics simulation on evaporation molecules in a vapor-liquid equilibrium state  [Not invited]

  Kazumichi Kobayashi, Kazumasa Hori, Hisao Yaguchi, Masao Watanabe

  THE 29TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS  2014/07  Xi'an, China 

  AIP Conf. Proc. 1628, 404 (2014); http://dx.doi.org/10.1063/1.4902621
• Numerical analysis of kinetic boundary conditions at net evaporation/condensation interfaces in various liquid temperatures based on mean-field kinetic theory  [Not invited]

  Misaki Kon, Kazumichi Kobayashi, Masao Watanabe

  THE 29TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS  2014/07  Xi'an, China 

  AIP Conf. Proc. 1628, 398 (2014); http://dx.doi.org/10.1063/1.4902620
• Acoustic Characteristics of Compressible Bubbly Liquids: Study Based on Equation of Motion of Spherical Bubbles  [Not invited]

  Junya KAWAHARA, Kazumichi KOBAYASHI, Masao WATANABE

  8th International Conference on Multiphase Flow  2013/05 

  No. 260, Total 5 pages
• Numerical simulations of impact pressure generated by single-droplet impact  [Not invited]

  Yuki Tatekura, Kazumichi Kobayashi, Masao Watanabe

  8th International Conference on Multiphase Flow  2013/05 

  No. 521, Total 5 pages
• Numerical analysis of nonequilibrium phase change phenomena between two liquid slabs with different temperature  [Not invited]

  Kon M, Kobayashi K, Watanabe M

  13th UK Heat Transfer conference  2013 

  No. 41, Total 6 pages, 2013
• Numerical analysis of vapor-liquid two-phase system based on the Enskog-Vlasov equation  [Not invited]

  Kazumichi Kobayashi, Kotaro Ohashi, Masao Watanabe

  THE 28TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS  2012/07 

  AIP Conf. Proc.
• Nonlinear Resonant Gas Oscillation Accompanied with Evaporation and Condensation  [Invited]

  Masashi Inaba, Takeru Yano, Kazumichi Kobayashi, Masao Watanabe

  THE 28TH INTERNATIONAL SYMPOSIUM ON RAREFIED GAS DYNAMICS  2012/07 

  【INVITED】AIP Conf. Proc.
• Resonant Gas Oscillation with Evaporation and Condensation  [Not invited]

  M. Inaba, T. Yano, M. Watanabe, K. Kobayashi

  19th International Symposium on Nonlinear Acoustics  2012 

  AIP Conf. Proc., No. 1474, pp.79-82, (2012).
• Derivation of Nonlinear Wave Equations for Ultrasound Beam in Nonuniform Bubbly Liquids  [Not invited]

  T. Kanagawa, T. Yano, J. Kawahara, K. Kobayashi, M. Watanabe, S. Fujikawa

  19th International Symposium on Nonlinear Acoustics  2012 

  AIP Conf. Proc.,No. 1474, pp.143-146, (2012).
• Innovative Ultra-Low Environmental Load Cleaning Method Using Steam-Water Mixed Spray: II. Micro-Scale Approach  [Not invited]

  M. Watanabe, K. Kobayashi, T. Sanada

  6th Japanese-European Two-Phase Flow Group Meeting  2012 

  Total 6 pages (CD-ROM), (2012)
• Innovative Ultra-Low Environmental Load Cleaning Method Using Steam-Water Mixed Spray: I. Macro-Scale Approach  [Not invited]

  T. Sanada, M. Watanabe, K. Kobayashi

  6th Japanese-European Two-Phase Flow Group Meeting  2012 

  Total 6 pages (CD-ROM)
• Droplet Impact as an Elementary Process of Physical Cleaning  [Not invited]

  K. Kobayashi, R. Uemura, M. Watanabe, T. Sanada, A. Hayashida

  9th International Conference on Fluid Dynamics  2012 

  Total 2 pages (CD-ROM), (2012).
• High-Speed Droplet Impact as an Elementary Process of Physical Cleaning  [Not invited]

  Toshihide Fujikawa, Yuuki Tatekura, Kazumichi Kobayashi, Toshiyuki Sanada, Atsushi Hayashida, Masao Watanabe

  ECS Transactions  2011/10  The Electrochemical Society
   

  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 plate 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 also spreads obliquely upward. The obliquely upward flow field may also contribute in advecting removed particles or stripped resists away from the original place.
• Ultrasound Beam Radiated From Circular Piston in Bubbly Liquids: Nonlinear Analysis for Envelope of Short Waves With Diffraction Effect  [Not invited]

  J. Kawahara, K. Kanagawa, T. Yano, K. Kobayashi, M. Watanabe, S. Fujikawa

  ASME-JSME-KSME 2011 Joint Fluids Engineering Conference  2011 

  Paper No. AJK2011-33019, pp. 251-256 (2011).
• Nonlinear Propagation of Sound Beam in Nonuniform Bubbly Liquids  [Not invited]

  T. Kanagawa, J. Kawahara, T. Yano, K. Kobayashi, M. Watanabe, S. Fujikawa

  ASME-JSME-KSME 2011 Joint Fluids Engineering Conference  2011 

  Paper No. AJK2011-33017, pp. 237-241 (2011).
• High-Speed Droplet Impact as an Elementally Process of Physical Cleaning  [Not invited]

  T. Fujikawa, Y. Tatekura, K. Kobayashi, T. Sanada, A. Hayashida, M. Watanabe

  ECS Meeting  2011 

  ECS Transaction, Vol.41, pp. 67-74 (2011).
• Numerical Analysis of Shock-Bubble Interactions near Tissue Boundaries  [Not invited]

  Kazumichi Kobayashi

  6th Japan-Taiwan Workshop on Mechanical and Aerospace Engineering  2011 

  Total 8 pages(CD-ROM), (2011).
• Direct Numerical Simulations of Bubble Collapse near a Tissue Surface with the Ghost Fluid Method  [Not invited]

  H. Takahira, K. Kobayashi

  157th meeting of Acoustic Society of America  2009 

  Journal of Acoustic Society of America, 124, 2712
• Influence of Shock-Bubble and Bubble-Bubble Interactions on the Collapse of a Cluster of Bubbles  [Not invited]

  K. Kobayashi, Y. Jinbo, H. Takahira

  7th International Symposium of Cavitation (Cav2009)  2009 

  Total 11 pages (CD-ROM), No.53, (2009)
• Numerical Investigations of Interactions between Shock Waves and Bubbles near Tissue Surface Using the Ghost Fluid Method  [Not invited]

  S. Syu, T. Matsuno, K. Kobayashi, H. Takahira

  7th JSME-KSME Thermal and Fluid Engineering Conference  2008 

  Total 2 pages (CD-ROM，No.E322), (2008)
• Molecular Gas Dynamics Simulations for the Collapse of Gas or Vapor Bubbles  [Not invited]

  K. Kobayashi, H. Takahira

  7th JSME-KSME Thermal and Fluid Engineering Conference  2008 

  Total 2 pages (CD-ROM, No.E313), (2008).
• Flow Structure and Bubble Fission of Gas-Liquid Two-Phase Venturi Tube Flows  [Not invited]

  K. Umeyama, K. Ikema, K. Kobayashi, H. Takahira

  7th JSME-KSME Thermal and Fluid Engineering Conference  2008 

  Total 2 pages (CD-ROM，No.E122), (2008).
• Molecular Gas Dynamics Simulation of the Collapse of Condensable Gas bubbles  [Not invited]

  K. Kobayashi, H. Takahira

  Cavitation in Turbo-Machinery & Medical Applications  2008 

  pp.204-209(CD-ROM), (2008)
• Numerical Analysis of Shock-Bubble Interactions near Boundaries Using the Ghost Fluid Method  [Not invited]

  K. Kobayashi, T. Matsuno, S. Syu, H. Takahira

  Cavitation in Turbo-Machinery & Medical Applications  2008 

  pp.190-194, (CD-ROM), (2008).
• Condensation Coefficient of Water in a Weak Condensation State  [Not invited]

  K. Kobayashi, S. Watanabe, D. Yamano, T. Yano, S. Fujikawa

  1st International Colloquium on Dynamics, Physics and Chemistry of Bubble and Gas-Liquid Boundaries  2007 

  Total 10 pages (CD-ROM), (2007).
• Shock-Tube-Deduced Condensation Coefficients of Methanol and Water Vapors  [Not invited]

  S. Watanabe, K. Kobayashi, M. Inaba, T. Yano, S. Fujikawa

  International Symposium on Advanced Fluid/Solid Science and Technology in Experimental Mechanics  2006 

  Total 5 pages (CD-ROM, No.A10-4),(2006)
• Molecular Gas Dynamics Approaches to Interfacial Phenomena Accompanied with Condensation  [Not invited]

  S. Mikami, K. Kobayashi, T. Ota, S. Fujikawa, T. Yano, M. Ichijo

  ECI International Conference on Heat Transfer and Fluid Flow in Microscale  2005 

  Total 4 pages (CD-ROM, No.70), (2005)
• A New Approach for Determination of Condensation Coefficient of Methanol by Combining Molecular Gas Dynamics Study and Shock Tube Experiment  [Not invited]

  K. Kobayashi, S. Fujikawa, T. Yano

  6th World Conference on Experimental Heat Transfer, Fluid Mechanics, and Thermodynamics  2005 

  Total 5 pages (CD-ROM, No.7-b-7), (2005).
• Numerical Computations of Vapor Condensation in Vapor-Liquid Nonequilibrium State at Shock Tube Endwall  [Not invited]

  K. Kobayashi, T. Yano, S. Fujikawa

  5th International Conference on Multiphase Flow  2004 

  Total 9 pages (CD-ROM, No.413), (2004).
• Numerical Analysis of Condensation Process of a Polyatomic Vapor behind a Reflected Shock Wave Based on the Kinetic Theory of Gases  [Not invited]

  K. Kobayashi, T. Yano, S. Fujikawa

  15th International Symposium on Transport Phenomena  2004 

  Total 5 pages (CD-ROM, No.101), (2004).
• Numerical Study of Condensation of a Polyatomic Vapor by a Shock Wave Based on the Kinetic Theory of Gases  [Not invited]

  T. Yano, K. Kobayashi, S. Fujikawa

  4th ASME/JSME Joint Fluids Engineering Conference  2003 

  Total 6 pages (CD-ROM, No. FEDSM2003-45022), (2003).

MISC

• 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  2021/09  [Refereed]
  
• 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  2020/02  [Refereed][Not invited]
  
• 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  2020/02  [Refereed][Not invited]
  
• 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  2019/09  [Refereed][Not invited]
  
• 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  2019/07  [Refereed][Not invited]
  
• 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  2019/07  [Refereed][Not invited]
  
• 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  2019/05  [Refereed][Not invited]
  
• 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)  2019/05  [Refereed][Not invited]
  
• 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)  2019/05  [Refereed][Not invited]
  
• Correction to: 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)  1005  -1005  2019/04  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Not refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  2017/10  [Refereed][Not invited]
  
• Influence of condensation coefficient on spherical bubble collapse with evaporation and condensation

  森川 昌太郎, 立藏 祐樹, 小林 一道, 藤井 宏之, 渡部 正夫, 佐々木 浩一  ながれ : 日本流体力学会誌 = Nagare : journal of Japan Society of Fluid Mechanics  36-  (2)  105  -108  2017/04  [Not refereed][Not invited]
  
• 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  [Not refereed][Not invited]
  
• 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  [Not refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  2016/12
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  2016  [Refereed][Not invited]
   

  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  2016  [Refereed][Not invited]
   

  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  2016  [Refereed][Not invited]
   

  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.
• 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"  2015/09/13  

  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.
• 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"  2015/09/13  

  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.
• 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  2015
• 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  [Not refereed][Not invited]
  
• 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  [Not refereed][Not invited]
  
• 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  [Not refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 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  [Not refereed][Not invited]
  
• 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  2015  [Refereed][Not invited]
   

  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.
• Chapter 5 : Shock Tube Experiment of Evaporation and Condensation

  小林 一道, 藤川 重雄  ながれ : 日本流体力学会誌 = Nagare : journal of Japan Society of Fluid Mechanics  33-  (6)  543  -548  2014/12
• Report of JSMF Symposium on Multiphase Flow 2014

  村井 祐一, 小林 一道  混相流  28-  (4)  483  -486  2014/12
• Chapter 4 Application of Molecular Gas Dynamics to Evaporation and Condensation

  Kazumichi Kobayashi, Shigeo Fujikawa, Graduate School of Engineering Hokkaido University, Graduate School of Engineering Hokkaido University  ながれ : 日本流体力学会誌 = Journal of Japan Society of Fluid Mechanics  33-  (5)  453  -459  2014/10/25
• 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  2014  [Refereed][Not invited]
   

  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  2014  [Refereed][Not invited]
   

  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.
• 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"  2013/09/08  

  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.
• 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"  2013/09/08  

  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.
• 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  2013/08/26
• 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  2013/08  [Not refereed][Not invited]
  
• 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  [Refereed][Not invited]
  
• 304 Numerical analysis of high-speed droplet spray flow in cleaning nozzle

  Tamura Toshiyuki, Kawahara Junya, Kobayashi Kazumichi, Watanab Masao  北海道支部講演会講演概要集  2012-  (51)  83  -84  2012/10/20
• 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  2012  [Refereed][Not invited]
   

  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  2012  [Not refereed][Not invited]
   

  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.
• Kinetic Theory for Flow Phenomena Accompanied with Evaporation/Condensation at a Vapor-Liquid Interface

  小林 一道  公益社団法人応用物理学会界面ナノ電子化学研究会NICE : 講演集  11-  21  -26  2012
• 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  2012  [Refereed][Not invited]
   

  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.
• 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  2012  [Refereed][Not invited]
   

  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 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  2012  [Refereed][Not invited]
   

  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  2012  [Refereed][Not invited]
   

  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].
• 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"  2011/09/11  

  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.
• 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"  2011/09/11  

  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.
• 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"  2011/09/11  

  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.
• Application of multigrid ghost fluid method to the interaction of shock waves with bubbles in liquids

  Kazumichi Kobayashi, Yoshinori Jinbo, Hiroyuki Takahira  Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B  77-  (773)  20  -32  2011  [Refereed][Not invited]
   

  A new numerical method based on the ghost fluid method was developed for compitssible two-phase flows the idea of athptive mesh refinement with multigrid was implemented in the method. In the method, interpolation tecimiques between multiple grids near interfaces were also proposed. The present techniques are effective in diminishing the numerical instability caused by the discontinuity of physical variables across the interfaces. The bubble collapse induced by the interaction of an incident shock with a gas bubble in water was simulated with the present multigrid ghost fluid method. We have succeeded in capturing the fine interface and vortex structure during the collapsing and rebounding stage. The mass conservation is improved with the adaptive mesh refinement combined with the hybrid particle level set method. Also, the interaction of an incident shock wave with a gas bubble near a deformable boundary was simulated successfully with the method in which the motions of three phases, i.e., the gas inside the bubble, the ambient liquid, and the wall material, are taken into consideration. © 2011 The Japan Society of Mechanical Engineers.
• 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  2010/11/07
• 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  2010/09/23
• 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  2010/09/23
• 1016 Numerical Analysis for Bubble Collapse near a Gelatin Surface Using Multi-Grid Ghost Fluid Method

  JINBO Yoshinori, SYU Sei, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2010-  (85)  "10  -16"  2010/03/16
• 1020 Influence of Bubble-Bubble lnteradiononthe Propagation of Pressure Waves in Gas-Liquid Two-Phase Flows

  SAYOU Akihito, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2010-  (85)  "10  -26"  2010/03/16
• 1023 Bubble Deformation and Formation of Liquid Jet in Gas-Liquid Two-Phase Venturi Flow

  KOBAYASHI Kazumichi, UMEYAMA Kazuya, NISHI Wataru, NOGAMI Masanori, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2010-  (85)  "10  -29"  2010/03/16
• S0507-2-3 Experimental Investigation on Bubble Deformation in a Contraction Tube Flow

  NISHI Wataru, NOGAMI Masanori, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  The proceedings of the JSME annual meeting  2010-  249  -250  2010  

  The bubble deformation in a gas-liquid contraction tube flow is observed with a high-speed camera to understand the mechanism of the bubble fission in the tube. It is shown that the surface instability occurs on the tip of a large bubble above the throat, which leads to the continuous detachment of small bubbles into the throat. Two kinds of liquid jets, ie, the forward jet and the counter jet, occur on the surface of small bubble in the throat. The result shows that the forward jet becomes faster as the bubble is pinched off more upstream. The forward jet can be caused by the pressure gradient behind the bubble. The result also shows that the counter jet occurs only when the L/R is small when L is the distance between the upstream and downstream bubbles and R is the bubble radius. The counter jet is caused by the deformation due to the bubble-bubble interaction.
• S0507-2-1 Numerical Simulations of Interactions of Shock Waves with In-line Bubbles

  MORIMOTO Mitsuhiro, JINBO Yoshinori, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  The proceedings of the JSME annual meeting  2010-  245  -246  2010  

  The present study is concerned with the interaction of an incident shock wave with in-line two bubbles by using the multi-grid ghost fluid method. The influence of the bubble-bubble distance on the formation of the liquid jets and the shock waves from the collapsing bubbles is investigated. It is shown that the collapse of the upstream bubble is decelerated by the rarefaction wave caused by the reflection of the incident shock wave at the surface of the downstream bubble. The shock waves generated by the collapse of the upstream bubble accelerate the collapse of the downstream bubble, which leads to the generation of higher internal gas pressure and faster liquid-jet velocity from the downstream bubble. It is also shown that there exists an initial bubble-bubble distance where the collapse of the downstream bubble is most accelerated.
• Numerical Simulations of Two-Phase Flow in Microfluidic Network

  NIKI Kazuhiro, KOBAYASHI Kazumichi  日本流体力学会年会講演論文集  2010-  97  -97  2010  

  In the present study, numerical simulations are conducted for the gas-liquid two-phase flow in a microfluidic network using a compact model proposed by F. Jousse et al. The aim of the present study is to examine the influence of bubble behavior (dispersed phase) on the flow rates in a microfluidic network. The result shows that the flow rates in the microfluidic network can be controled by changing the void fraction of dispersed phase at the inlet. Also the compact model is capable of explaining the experimental results of Microfluidic bubble logic shown by M. Prakash et al. qualitatively.
• 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<
• Novel 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.
• 2006 Collapse of In-Line Bubbles near a Tissue Surface : Effects of Bubble-Bubble Interaction on a Tissue Surface

  JINBO Yoshinori, SYU Sei, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  The Computational Mechanics Conference  2009-  (22)  554  -555  2009/10/10
• 2005 Numerical Simulations of Bubble Collapse near a Tissue Surface Using the Multi-Grid Ghost Fluid Method : Interface Capturing with Two Level Set Functions

  KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  The Computational Mechanics Conference  2009-  (22)  552  -553  2009/10/10
• 1004 Experimental Investigation on Bubble Collapse and Propagation of Pressure Wave for Gas-Liquid Two-Phase Flow in Venturi Tube

  NOGAMI Masanori, UMEYAMA Kazuya, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2009-  (84)  "10  -4"  2009/03/16
• 1003 Numerical Simulations for Bubble Deformation in Convergent Tube Using Ghost Fluid Method

  SHIBAHARA Daikichi, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2009-  (84)  "10  -3"  2009/03/16
• 1012 Molecular Dynamicis Study for Evaporation and Condensation Processes of Thin Liquid Film on Solid Wall

  YAMAGUCHI Yoshiaki, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2009-  (84)  "10  -12"  2009/03/16
• 1006 Growth of Microbubbles Covered with Surfactant

  IRIE Maya, SAYO Akihito, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2009-  (84)  "10  -6"  2009/03/16
• 28aTK-11 Molecular dynamics simulations for evaporation and condensation phenomena at thin liquid film on solid wall

  Kobayashi Kazumichi, Yamaguchi Yoshiaki, Takahira Hiroyuki  Meeting abstracts of the Physical Society of Japan  64-  (1)  289  -289  2009/03/03
• Kinetic boundary condition at a vapor-liquid interface of thin liquid layer using the molecular dynamics method

  KOBAYASHI Kazumichi, YAMAGUCHI Yoshiaki, TAKAHIRA Hiroyuki  日本流体力学会年会講演論文集  2009-  218  -218  2009  

  In the present study, the kinetic boundary condition for the Boltzmann equation at a vapor-liquid interface of thin liquid layer on a solid wall is investigated using molecular dynamics simulations. The vapor and liquid are composed of argon molecules and the solid wall is composed of platinum molecules. Two kinds of energy parameter of L-J potential between argon and platinum are chosen for the simulations with different wetability. The results show that the kinetic boundary condition for the vapor-liquid system is applicable to the vapor-liquid-solid system as long as the liquid layer is about 6 times larger than the molecular diameter because the velocity components in every direction obey the Maxwellian and the evaporation coefficient for the vapor-liquid-solid system coincides with that for the vapor-liquid system.
• J0201-1-4 Influence of Gas Diffusion on Growth and Shrinkage of a Microbubble with Surfactant Layers

  SAYOU Akihito, IRIE Maya, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  The proceedings of the JSME annual meeting  2009-  103  -104  2009  

  The growth and shrinkage of surfactant-coated microbubbles are observed with a high-speed video camera. The observed bubble motion is compared with the simulation in which the dynamic surface tension and the variation of gas permeation resistance of surfactant layers are considered. The simulation is in good agreement with the experiment. It is shown that when the microbubble grows under pressure reduction, the gas diffusion from the surrounding liquid to bubble inside is suppressed by the increase of the surface tension, while it is promoted by the decrease of the gas permeation resistance. On the other hand, the bubble shrinkage due to gas diffusion after pressure increase is strongly affected by the increase of the gas permeation resistance. The variations of both the surface tension and the gas permeation resistance determine the diffusion process of microbubbles.
• 754 Bubble Collapse in the Vicinity of a Tissue Surface : Numerical Simulation with the Ghost Fluid Method

  SYU Sei, MATSUNO Takahiro, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  The Computational Mechanics Conference  2008-  (21)  871  -872  2008/11/01
• (8)衝撃波管管端でのメタノール蒸気の凝縮過程に関する分子気体力学解析(論文,日本機械学会賞〔2007年度(平成19年度)審査経過報告〕)

  矢野 猛, 小林 一道, 藤川 重雄  日本機械学會誌  111-  (1074)  375  -375  2008/05/05
• 509 Numerical Investigations of Bubble Collapse near a Gelatin Surface Using the Ghost Fluid Method

  SYU Sei, MATSUNO Takahiro, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2008-  (83)  "5  -11"  2008/03/14
• 508 Axi-symmetric Numerical Simulations of Shock/Bubble Interactions near Mercury-Glass Boundaries

  MATSUNO Takahiro, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2008-  (83)  "5  -10"  2008/03/14
• 403 Experimental Investigation on the Mechanism of Bubble Fission in Gas-Liquid Two-Phase Flow Using Venturi Tube

  UMEYAMA Kazuya, IKEMA Kengo, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2008-  (83)  "4  -3"  2008/03/14
• 518 Numerical Simulations for Bubble Collapses with Phase Change Based on Molecular Gas Dynamics

  KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  関西支部講演会講演論文集  2008-  (83)  "5  -25"  2008/03/14
• 1616 Numerical Investigations of Bubble Collapse near a Tissue Surface Using the Ghost Fluid Method

  SYU Sei, MATSUNO Takahiro, KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  The proceedings of the JSME annual meeting  2008-  29  -30  2008  

  In the present study, numerical simulations are conducted for the collapse of an air bubble near a tissue surface by using an improved ghost fluid method. A tissue is modeled with a gelatin that was used in the experiment by Kodama and Takayama. The bubble collapse is induced by the interaction between a bubble and an incident shock wave. A flat shock wave profile and an exponential one based on the experimemt by Kodama and Takayama are utilized, and the influence of the shock wave profile on the dynamical motion of the bubble and gelatin is investigated. It is shown that the gelatin surface is depressed by the shock waves generated from the bubble. The penetration of the bubble into the depression of the gelatin, which was demonstrated in the experiment by Kodama and Takayama, is simulated successfully. The results also show that the collapse time of a bubble is longer and the width of the depression is thinner when the shcok wave with the exponential profile interacts with the bubble.
• 1115 Numerical Simulations of Single Bubble Dynamics Accompanied with Phase Change Based on Molecular Gas Dynamics(2)

  KOBAYASHI Kazumichi, TAKAHIRA Hiroyuki  Fluids engineering conference ...  2007-  "1115  -1"-"1115-4"  2007/11/17  

  The collapse and rebound of a spherical bubble filled with a noncondensable gas or condensable gas (vapor) were investigated by combining bubble dynamics and molecular gas dynamics. The polyatomic version of Gaussian-BGK Boltzmann equation was utilized for a gases vapor inside the bubble, while Fujikawa & Akamatsu's equation was utilized for the motion of the bubble. These equations were solved numerically with the kinetic boundary condition including a condensation coefficient that is an important parameter for phase change processes. The result shows that the condensation at a vapor-liquid interface of a vapor bubble is essential for the mechanism of collapse and rebound of the bubble.
• 206 A Method of Evaporation-Coefficient Measurement for Liquid by Weak Sound Wave

  NAKAMURA Shigeto, KOBAYASHI Kazumichi, INABA Masashi, YANO Takeru, FUJIKAWA Shigeo  関西支部講演会講演論文集  2007-  (82)  "2  -6"  2007/03/16
• On Receiving the Best Presentation Award

  KOBAYASHI K.  熱物性 : Japan journal of thermophysical properties  21-  (1)  55  -55  2007/02/28
• 303 Establishment of Kinetic Boundary Conditions of Methanol and Water on the Basis of Molecular Gas Dynamics Analysis and Shock Tube Experiment(2)

  KOBAYASHI Kazumichi, WATANABE Shunsuke, INABA Masashi, YANO Takeru, FUJIKAWA Shigeo, ICHIJO Makoto  Fluids engineering conference ...  2006-  "303  -1"-"303-4"  2006/10/28  

  The present paper aims at establishing kinetic boundary conditions of methanol and water through the determination of condensation coefficients based on molecular gas dynamics analysis and shock tube experiment in weak vapor-liquid nonequilibrium states. The results show that, when the ratio of vapor pressure to saturated vapor pressure at the interface is close to unity, values of condensation coefficients of methanol and water equal to evaporation coefficient estimated by the resent molecular dynamics analysis. As the ratio becomes large, the condensation coefficients decrease. The pressure ratio dependency of a condensation coefficient is explained by the molecular gas dynamics analysis.
• 303 Establishment of Kinetic Boundary Conditions of Methanol and Water on the Basis of Molecular Gas Dynamics Analysis and Shock Tube Experiment(1)

  KOBAYASHI Kazumichi, WATANABE Shunsuke, INABA Masashi, YANO Takeru, FUJIKAWA Shigeo, ICHIJO Makoto  Fluids engineering conference ...  2006-  "303  -a"  2006/10/28
• Preliminary 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  -+  2005/09  [Not refereed][Not invited]
  
• 925 Determination of Condensation Coefficient for Methanol : Numerical Analysis Based on Molecular Gas Dynamics for Shock Tube Experiment

  KOBAYASHI Kazumichi, MIKAMI Satoru, OTA Tatsuki, YANO Takeru, FUJIKAWA Shigeo, ICHIJO Makoto  The proceedings of the JSME annual meeting  2005-  87  -88  2005  

  We perform the determination of the condensation coefficient for methanol by combining a numerical analysis based on the molecular gas dynamics and shock tube experiment. In the numerical analysis, the boundary condition for the Boltzmann equation at the vapor liquid interface is rewritten using the net mass flux obtained from the shock tube experiment. Thereby, the condensation coefficient is determined by the vapor-liquid system. The result shows that the value of the condensation coefficient for methanol ranges from 0.7 to 0.9, and it is close to that of the evaporation coefficient evaluated by the recent molecular dynamics simulation.
• 924 Determination of Condensation Coefficient for Methanol : Measurement of Liquid film Growth By using Optical Interferometer at the Shock Tube Endwall

  MIKAMI Satoru, OTA Tatsuki, KOBAYASHI Kazumichi, FUJIKAWA Sigeo, YANO Takeru, ICHIJO Makoto  The proceedings of the JSME annual meeting  2005-  85  -86  2005  

  The condensation coefficient is obtained by combining a shock tube experiment and the corresponding numerical analysis based on the Gaussian-BGK Boltzmann equation. In the experiment, the liquid film growth on the shock tube endwall behind the reflected shock wave is measured with a high accuracy by an optical interferometer. The interferometer system is improved, which enables us to combine the experiment and numerical analysis more closely. The results show that the condensation coefficient of methanol takes values from 0.7 to 0.9 in nonequilibrium states, and the values are close to that of evaporation coefficient evaluated by molecular dynamics simulations.
• Condensation of methanol vapor onto its liquid film on a solid wall behind a reflected shock wave

  T Yano, K Kobayashi, S Fujikawa  Rarefied Gas Dynamics  762-  208  -213  2005  [Refereed][Not invited]
   

  On the basis of the polyatomic gas version of the Gaussian-BGK model of the Boltzmann equation, we shall numerically analyze the condensation of methanol vapor onto its liquid film on an endwall of the shock tube induced by the pressure elevation due to a reflected shock wave. By comparing the numerical results with experimental ones, we can determine the value of condensation coefficient in various nonequilibrium conditions. It is shown that at around room temperature, the condensation coefficient of methanol vapor is almost unity when the condensation is sufficiently weak. In this case, the asymptotic analysis for the steady problem gives an appropriate estimation for the rate of the growth of the liquid film thickness.
• 28pWD-12 Numerical analysis of a film condensation phenomenon of a polyatomic vapor based on molecular gas dynamics

  Kobayashi K., Yano T., Fujikawa S.  Meeting abstracts of the Physical Society of Japan  59-  (1)  299  -299  2004/03/03
• Numerical Analysis of Plane Shock Wave in Polyatomic Molecule Gas Based on Molecular Gas Dynamics

  KOBAYASHI Kazumichi, YANO Takeru, FUJIKAWA Shigeo  The proceedings of the JSME annual meeting  2004-  373  -374  2004  

  Numerical analysis is performed for a normal shock wave in a polyatomic molecule gas based on molecular gas dynamics, where the polyatomic gas is taken to be nitrogen. We adopt the polyatomic version of Gaussian-BGK Boltzmann equation for nitrogen gas and it is solved numerically with a finite difference method. The results agree well with the experimental results by Robben and Talbot (1966) at the shock Mach number 1.71. Furthermore, we examine the transition of rotational energy in the shock wave in terms of velocity distribution functions.
• Numerical Simulations of Condensation Phenomena of a Polyatomic Vapor behind a Reflected Shock Wave

  KOBAYASHI Kazumichi, YANO Takeru, FUJIKAWA Shigeo  北海道支部講演会講演概要集  2003-  (43)  196  -197  2003/09/28
• Numerical Analysis of Condensation Phenomenon of Methanol Vapor in a Shock Tube

  KOBAYASHI Kazumichi, YANO Takeru, FUJIKAWA Shigeo  Fluids engineering conference ...  2003-  94  -94  2003/09/18
• Molecular Gas Dynamics Simulation of Phase Change of Polyatomic Molecule Vapor in Nonequilibrium State

  KOBAYASHI Kazumichi, YANO Takeru, FUJIKAWA Shigeo  北海道支部講演会講演概要集  2002-  (42)  114  -115  2002/10/05

Awards & Honors

• 2023/07 Fluids Engineering DIvision, the Japan Society of Mechanical Engineers Frontier Award
   Molecular Fluid Dynamics Analysis of Heat and Mass Transport at Gas-Liquid Interface 

  受賞者: Kazumichi Kobayashi
• 2021/04 Nature Portfolio Top 100 in Physics
   Evaporation coefficient and condensation coefficient of vapor under high gas pressure conditions 

  受賞者: Kotaro Ohashi;Kazumichi Kobayashi;Hiroyuki Fujii;Masao Watanabe
• 2008/04 Japanese Society of Mechanical Engineering JSME Medal for Outstanding Pape
   Molecular Gas Dynamics of Condensation Processes of Methanol Vapor behind a Reflected Shock Wave in a Shock Tube
• 2007/03 Japanese Society of Thermophysical Properties Best Presentation Award
   衝撃波管管端で起こる膜状凝縮によって測定された水の凝縮係数 

  受賞者: Kazumichi Kobayashi
• 2005/06 The 1st CRIS International Symposium on Computational Science and Neuroscience Top Poster Award
   Determination of Condensation Coefficient of Methanol by Combining Molecular Gas Dynamics Simulation and Shock Tube Experiment 

  受賞者: Kazumichi Kobayashi

Research Grants & Projects

• Relaxation of intramolecular vibrations of solvents by infrared excitation and elucidation of effective infrared absorption wavelength band for drying solvent

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2022/04 -2025/03 

  Author : 戸谷 剛, 小林 一道
• Molecular Fluid Dynamics of AWAI

  Japan Science and Technology Agency：Presto

  Date (from‐to) : 2021/10 -2025/03
• 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

  日本学術振興会：科学研究費助成事業 基盤研究(B)

  Date (from‐to) : 2020/04 -2023/03 

  Author : 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．
• Influence of the interference effects on radiative transfer in dense colloidal suspensions

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2020/04 -2023/03 

  Author : 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。
• Elucidation of non-equilibrium phase change at gas-liquid interface mechanism for mixture gas and its application to molecular multi-phase fluid dynamics

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)

  Date (from‐to) : 2020/04 -2023/03 

  Author : 小林 一道

   

  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．
• 赤外線連続照射による気液界面での分子内振動の緩和と溶剤乾燥に効果的な吸収帯の解明

  日本学術振興会：科学研究費補助金

  Date (from‐to) : 2019/04 -2022/03 

  Author : 戸谷剛
• Gas molecular behaviors in pore

  corporation：Joint Research

  Date (from‐to) : 2020/07
• Gas molecular behaviors in pore

  corporation：Joint Research

  Date (from‐to) : 2019/12 -2020/06
• 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

  日本学術振興会：科学研究費補助金

  Date (from‐to) : 2018/04 -2020/03 

  Author : Masao Watanabe
• 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

  日本学術振興会：科学研究費補助金

  Date (from‐to) : 2017/04 -2020/03 

  Author : 渡部正夫
• 超音波と微細気泡を用いた混合液体分離技術の開発

  公益信託小野音響学研究助成基金：公益信託小野音響学研究助成基金

  Date (from‐to) : 2019/04 -2019/12 

  Author : 小林一道
• 2成分混合気体の気体論境界条件の決定とその応用

  日本学術振興会：科学研究費補助金

  Date (from‐to) : 2016/04 -2019/03 

  Author : 小林一道
• Condensation effect on high-speed liquid-film flow instability at a liquid-droplet impact on a solid surface in a vaporous environment

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2014/04 -2017/03 

  Author : 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.
• 平均場運動論理論による高速移動気液界面における非定常熱・物質輸送現象の解明

  日本学術振興会：科学研究費補助金

  Date (from‐to) : 2014/04 -2016/03 

  Author : 渡部正夫
• 気体分子運動論による気液二相流体の高精度計算手法の構築と界面ダイナミクスへの展開

  Japan Society for the Promotion of Science：Grant-in-Aid for Scientific Research (KAKENHI)

  Date (from‐to) : 2013/04 -2016/03 

  Author : 小林一道
• 集束超音波と液面の相互作用による液体ジェット生成技術の開発

  ノーステック財団研究開発助成事業：若手研究人材育成事業

  Date (from‐to) : 2015/04 -2016/02 

  Author : 小林一道
• マイクロヒートポンプ内の相変化を伴う気液二流体流れの基礎研究

  北海道ガス：北海道ガス大学助成制度

  Date (from‐to) : 2013/04 -2014/03 

  Author : 小林一道
• Study on Transport phenomena at supercritical mixure interface by moelcular velocity distribution function and mean field kinetic theory

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2011/04 -2013/03 

  Author : Masao Watanabe

   

  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.
• 気液相変化を伴う界面境界条件の構築およびその流体力学への応用

  Japan Society for the Promotion of Science：Grant-in-Aid for Scientific Research (KAKENHI)

  Date (from‐to) : 2010/04 -2013/03 

  Author : Kazumichi Kobayashi

   

  気体－液体界面における素過程を考慮し，分子動力学や気体分子論の立場から流体体力学へ応用可能な境界条件のモデルを導出し流体力学シミュレーションへの応用を目指す．
• 単一液滴の抵抗低減に及ぼす周囲蒸気凝縮効果の考究による革新的洗浄法素過程の解明

  日本学術振興会：科学研究費補助金

  Date (from‐to) : 2010/04 -2013/03 

  Author : 渡部 正夫
• 気泡崩壊現象における極限物理の解明

  Japan Society for the Promotion of Science：Grant-in-Aid for Scientific Research (KAKENHI)

  Date (from‐to) : 2009/04 -2013/03 

  Author : 高比良 裕之
• 異なる三つの法則が支配する非平衡気液界面の分子輸送過程に関するマルチスケール展開

  Japan Society for the Promotion of Science：Japan Society for the Promotion of Science

  Date (from‐to) : 2009/04 -2011/03 

  Author : 藤川 重雄
• 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

  Japan Society for the Promotion of Science：Grant-in-Aid for Scientific Research (KAKENHI)

  Date (from‐to) : 2009/04 -2011/03 

  Author : 渡部 正夫
• Determination of evaporation and condensation coefficients and new approach for bubble dynamics using molecular dynamics and molecular gas dynamics

  Japan Society for the Promotion of Science：Grant-in-Aid for Scientific Research (KAKENHI)

  Date (from‐to) : 2007/04 -2009/03 

  Author : Kazumichi Kobayashi

   

  分子動力学および分子気体力学を用いて気液界面での蒸発・凝縮メカニズムの分子論的解明を行う。また、前述の研究から得られた知見を用いて気液界面で蒸発・凝縮現象を伴う気泡のダイナミクスに関する研究を行う．
• 分子気体力学解析と衝撃波管の実験による非平衡状態における気体論境界条件の確立

  日本学術振興会：特別研究員奨励費

  Date (from‐to) : 2006/04 -2007/03 

  Author : 小林一道
• Evaporation/Condensation Phenomena, Numerical Simulation of Kinetic Theory of Gases, Molecular Dynamics

Educational Activities

Teaching Experience

Committee Membership

• 2024/04 - Today   The Japanese Society of Fluid Mechanics   Representative committee member
• 2024/01 - Today   Japanese society of thermophysical properties   councillor
• 2023/04 - Today   Japanese Society of Mechanical Engineering   Executive Committee
• 2022/04 -2024/03   The Japan Society of Mechanical Engineering   Secretary, Technical Committee, Fluid Engineering Division
• 2023/04 -2023/08   The Japanese Society for Multiphase Flow   Comittee of symposium of multiphase flow
• 2020/04 -2022/03   The Japan Society of Fluid Mechanics   Delegate
• 2020/01 -2022/01   Japanese Society of Thermophysical Properties   Councillor