Fluid Structure Interaction Analysis of Aorta Using OpenFOAM and CalculiX
NARA Toshiki, TAKASHIMA Hideyoshi, LI Chenyu, TAKEDA Ryo, SASAKI Katsuhiko, KURODA Akiyoshi, YOKOYAMA Hiroichi, KAMIYA Hiroyuki
The Proceedings of The Computational Mechanics Conference, 2022.35, 15-05, The Japan Society of Mechanical Engineers, 2022
Japanese, Currently, biomechanical simulations of blood vessels and organs are widely used in medical research, and it is expected to realize rapid and accurate medical diagnosis by personalized biological simulations for each individual using high-speed and high-precision 3D modeling of the body internal geometry by Multi Detector-row Computed Tomography (MDCT) and Magnetic Resonance Imaging (MRI). In particular, biomechanical simulation approach using Open Source Software (OSS) has been developed for use in the medical field, and recently, its application to more challenging multiphysics simulation has been studied. However, OSS has many issues such as assurance of accuracy and validity of the analysis, the computation time and stability of Fluid-Structure Interaction (FSI), and the lack of analysis functions for complex phenomena. In particular, blood flow simulation using OpenFOAM, a fluid analysis OSS, has issues in the representation of blood pressure changes caused by pulsation and body movement, and the stability of coupled analysis in conjunction with other structural analysis software. In this study, we added the Windkessel model, which is one of the models for expressing blood pressure changes, to OpenFOAM and developed a two-way coupled multi-physics simulation approach using OpenFOAM and CalculiX. As an example of personalized biomechanical simulation, we applied the method to simulate blood flow in the thoracic aorta and evaluated its effectiveness.

Investigations into the Potential of using of Open Source CFD to analyze the Differences in Hemodynamic Parameters for Aortic Dissections (Healthy vs. Stanford Type A and B)　　　　　　　　　　　　　　　
Ryo Takeda, Fumiya Sato, Hiroichi Yokoyama, Katsuhiko Sasaki, Nobuyuki Oshima, Akiyoshi Kuroda, Hideyoshi Takashima, Chenyu Li, Shinya Honda, Hiroyuki Kamiya
Annals of Vascular Surgery, 2021, [Peer-reviewed]
English, Scientific journal

A Pilot Study on Pressure, Flow Rate and Wall Shear Stress within Healthy, Stanford A and B type Aortas using Open Source CFD　　　　　　　　　　　　　　　
Ryo Takeda, Fumiya Sato, Hiroichi Yokoyama, Katsuhiko Sasaki, Nobuyuki Oshima, Akiyoshi Kuroda, Hideyoshi Takashima, Chenyu Li
Annals of Vascular Surgery, 2021, [Peer-reviewed]
English

Experimental and Numerical Study on Phase Change Material (PCM) for Thermal Management of Mobile Devices
Yusuke Tomizawa, Katsuhiko Sasaki, Akiyoshi Kuroda, Ryo Takeda, Yoshihiko Kaito
Applied Thermal Engineering, 98, 320, 329, 2016, [Peer-reviewed]
English

111 Thermal deformation analysis of CF-A1 composite under temperature change considering the inner structure
YAMAMOTO Ken, SASAKI Katsuhiko, KURODA Akiyoshi, TAKEDA Ryo, KATAGIRI Kazuaki
The Proceedings of Conference of Hokkaido Branch, 2013, 0, 21, 22, The Japan Society of Mechanical Engineers, 2013, [Peer-reviewed]
Japanese

Measurement of Cooling Characteristic of Latent Heat Storage Emulsion Slurry
Ueki Yoshikazu, Kudou Kazuhiko, Kuroda Akiyoshi, Mochida Akeno, Oguma Masahito
Proceedings of thermal engineering conference, 2002, 461, 462, The Japan Society of Mechanical Engineers, 2002
Japanese, An experimental study was made to study the cooling characteristics of O/W emulsion slurry. While the slurry is cooled down, the temperature of the sample in an agitated tank was measured by a thermocouple, and the distribution of diameter of the emulsion particles was measured from the pictures captured by a microscope. As the result, it was shown that the temperature history during the cooling has two distinct flat phases. Diameter of the emulsion has strong effect in the temperature of the flat phase, when the diameter is longer, the temperature becomes high.

Analysis on inverse radiative load problem　　　　　　　　　　　　　　　
Kazuhiko Kudo, Akiyoshi Kuroda, Tatsuhiko Saito, Masahito Oguma
Proceedings of the International Conference on Inverse Problems in Engineering, 455, 461, ASME, 1998
English, International conference proceedings, A method to solve inverse radiative load problems are developed and the validity of the method has been demonstrated. In the present study, a two-dimensional rectangular furnace is treated in which a rectangular heating object is set within the furnace and is heated by several heater elements set along the furnace walls. The distributions of the heat flux and the temperature of the heater elements required to realize specified heat flux along the surface of the heating object are properly estimated by using the singular value decomposition method (SVD), when the condition number of the singular values is chosen properly.

Improvement of analytical method on radiative heat transfer in nongray media by Monte Carlo method　　　　　　　　　　　　　　　
Kazuhiko Kudo, Hiroshi Taniguchi, Akiyoshi Kuroda, Maromu Ohtaka, Hiroshi Kakota, Masakazu Obata
Heat Transfer - Japanese Research, 22, 6, 559, 572, 1993
English, Scientific journal, An accelerated method is developed for radiative heat-transfer analysis in nongray media by the Monte Carlo method. Instead of deciding all the parameters of each energy particle used in the Monte Carlo procedure by a stochastic method, the wave number assigned to each energy particle is determined by a deterministic method in the present study. This change in the Monte Carlo algorithm reduces the computation time to one-ninth of the original time. To reduce the amount of iteration required to converge the temperature profile in a nongray media layer, an acceleration factor is incorporated to determine the new values of temperature in each iterational loop. The value of the acceleration factor is found to be related to the optical thickness of each media element. By using an appropriate acceleration factor, the amount of iteration is reduced to one-fourth of the original. Moreover, the total computation time becomes 1/36 of the original by the two improvements.

Fluid-Structure Interaction Analysis of Aortic Dissection Using Open Source
CHEN Junnan, 佐々木克彦, 本田真也, 武田量, 大島伸行, 黒田明慈, 横山博一, LI Chenyu, 高嶋英厳, 日本機械学会計算力学講演会論文集(CD-ROM), 32nd, 2019

流体解析による大動脈解離後の血流評価および壁面せん断応力の推定
木島雄大, 武田量, 横山博一, 黒田明慈, 大島伸行, 佐々木克彦, 日本機械学会バイオフロンティア講演会講演論文集(CD-ROM), 28th, 2017

OS14-4 Phase Change Materials and High Thermal Conductive Materials for Thermal Management of Smart Phones(Semiconductor Devices and Electronic Packaging 2,OS14 Electronic and photonic packages,APPLICATIONS)
Tomizawa Yusuke, Sasaki Katsuhiko, Kuroda Akiyoshi, Kaito Yoshihiko, Abstracts of ATEM : International Conference on Advanced Technology in Experimental Mechanics : Asian Conference on Experimental Mechanics, 2015, 14, 210, 210, 04 Oct. 2015
The Japan Society of Mechanical Engineers, English

S0220304 Analysis of Stent Expansion Considering Blood Deformation Due to Pulse Flow
HOSHINO Amane, KURODA Akiyoshi, Sasaki Katsuhiko, Takeda Ryo, Mechanical Engineering Congress, Japan, 2015, "S0220304, 1"-"S0220304-5", 13 Sep. 2015
Stenting is a common treatment of stenosis. One of problems of stent treatment is restenosis. Local hemodynamic factor such as low wall shear stress (WSS) is one of the reasons for restenosis. Therefore, blood flow analyses have been performed to clarify the restenosis mechanism. Fluid-Structure Interaction (FSI) is used for blood flow analysis to consider the interaction between fluid pressure and structure deformation. In this research, the effects of the deformed vessel by stenting and pulsating flow are analyzed using FSI. The stent expansion analysis was performed to obtain the deformed shape using FEM analysis software ANSYS Mechanical APDL. FSI analysis was performed to examine the effect of a pulsating vessel using ANSYS Workbench. An initial stent model was made based on the shape of before the expansion. The expanded stent model was also made based on the shape of the expanded stent. To reveal the effect of pulsatile on the blood flow after the stenosis, two boundary conditions were employed; rigid wall and FSI. Inlet flow rate was assumed to be expressed by a periodic function to reproduce the pulsating flow in the carotid artery. The results of velocity, pressure difference and WSS are shown for each model and condition. In the case of rigid wall, WSS at the stenting site is reduced by the expansion of the vessel., The Japan Society of Mechanical Engineers, Japanese

B121 Thermal Management of Smart Phones Using Phase Change Materials (PCM)
Tomizawa Yusuke, Kuroda Akiyoshi, Sasaki Katsuhiko, Kaito Yoshihiko, Matsuda Kazuyuki, Procee[d]ings of Thermal Engineering Conference, 2014, "B121, 1"-"B121-2", 08 Nov. 2014
As smart phones become more complex, higher in performance and smaller in size, heat concentration at localized areas is becoming a problem. Phase change materials (PCM) have drawn attention as passive thermal management. In this study, simple experiments using PCM were conducted. The results showed that the saturation time increased with increase in the mass of PCM, and a relationship between the saturation time and the mass of PCM was a linear relation. Furthermore, the saturation time increased with decrease in the melting temperature of PCM. As a result, PCM is effective for the thermal management of smart phones., The Japan Society of Mechanical Engineers, Japanese

222 Numerical Analysis of Collision between a Liquid Droplet and a Solid Surface by Lattice Boltzmann Method
NATSUME Shinya, KURODA Akiyoshi, 北海道支部講演会講演概要集, 2014, 53, 43, 44, 27 Sep. 2014
The Japan Society of Mechanical Engineers, Japanese

H133 Surface Temperature of Smart Phone Case Using High Thermal Conductive Materials
Tomizawa Yusuke, Kuroda Akiyoshi, Sasaki Katsuhiko, Kaito Yoshihiko, Matsuda Kazuyuki, Procee[d]ings of Thermal Engineering Conference, 2013, 255, 256, 18 Oct. 2013
As smart phones become more complex, higher in performance and smaller in size, heat concentration at localized areas is becoming a problem. Therefore, the aim of this paper is to examine the effect of high thermal conductive materials for heat dissipation in order to solve this problem. The thermal conductivity of the outer case of the smart phone was changed using finite element method (FEM) to simulate high thermal conductive materials or composite materials with anisotropy. The maximum temperature gradually decreased and the minimum temperature gradually increased with increasing the thermal conductivity of the outer case. Moreover, the thermal conductivity in the longer direction of the smart phone was important for lowering the maximum temperature. In this paper, it is found that applying high thermal conductive materials to the outer case is effective for uniforming the heat dispersing., The Japan Society of Mechanical Engineers, Japanese

112 Bending Toughness of Silicon used for Solar Cells
FUKIYA Takafumi, SASAKI Katsuhiko, KURODA Akiyoshi, TAKEDA Ryo, 北海道支部講演会講演概要集, 2013, 52, 23, 24, 28 Sep. 2013
The Japan Society of Mechanical Engineers, Japanese

P-G1-1 Control of Orientation of VGCF Using Water Flow with Microfluidic device
Ohnogi Shigeru, Sasaki Katsuhiko, Kuroda Akiyoshi, Xu Zhang, Katagiri Kazuaki, Takahashi Norio, Nagai Akio, Ito Yohei, Kakitsuji Aushi, The Proceedings of the Symposium on Micro-Nano Science and Technology, 2012, 4, 191, 192, 21 Oct. 2012
There is an urgent need to enhance the energy efficiency of various instruments. Carbon fiber-containing aluminum composite is expected to improve the ability of heat dissipation of heat exchanger, and heat sink. Especially, both carbon nanotube (CNT) and vapor-grown carbon fiber (VGCF), which is a kind of carbon fiber, have high thermal conductivity in axial direction, because of its high aspect ratio. Therefore, alignment of carbon fibers is a key factor to fabricate high thermal conductive composites using CNT and VGCF. In this study, a micro-channel was successfully fabricated and the possibility to control the alignments of VGCF using the contraction of the water flow in the micro-channel was confirmed. The method may have a benefit to fabricate high thermal conductive composites containing CNT and VGCF., The Japan Society of Mechanical Engineers, Japanese

VGCF・CNTを含むアルミニウム高熱伝導複合材料を用いたIGBTクーリングシステムの伝熱解析
佐々木克彦, 黒田明慈, 片桐一彰, 片桐一彰, 高橋教雄, 高橋教雄, 永井明夫, 永井明夫, 伊藤洋平, 伊藤洋平, 垣辻篤, Thermophys Prop, 33rd, 320, 322, 03 Oct. 2012
Japanese

溝付チャネル内乱流と伝熱の数値解析
大西将気, 黒田明慈, 日本伝熱シンポジウム講演論文集(CD-ROM), 49th, ROMBUNNO.F311, 2012
Japanese

太陽電池パネルの熱変形のはんだ接続部への影響
安藤佑, 佐々木克彦, 黒田明慈, 日本機械学会北海道支部講演会講演概要集, 50th, 53, 54, 01 Oct. 2011
Japanese

液滴衝突現象における2相流計算手法の比較
黒田明慈, 中西健市郎, 日本機械学会北海道支部講演会講演概要集, 50th, 107, 108, 01 Oct. 2011
Japanese

J043011Simulation of Alignment of CNT by Water Flow for Aluminum/CNT Composites
Zhang Xu, Kuroda Akiyoshi, Sasaki Katsuhiko, KATAGIRI Kazuaki, KAKITSUJI Atsushi, Mechanical Engineering Congress, Japan, 2011, "J043011, 1"-"J043011-5", 11 Sep. 2011
Simulation of alignment of CNTs or VGCFs by the water contraction flow was carried out. The flow was reproduced using ANSYS CFX software and then the dynamic motion of CNTs transported by the flow was calculated. 2D contraction flow with upstream and downstream channel flows was used. And a CNT was modeled as a dumbbell-like element. The orientation angle of the elements at the end of the downstream flow channel was estimated. It is found that the ratio of upstream channel width to downstream channel width is the major factor for the alignment of the elements. And the absolute value of average angle 0.29 degree and minimum standard deviation 4.98 degree were obtained with upstream channel width 25 cm, contraction length 20 cm, downstream channel length 10 cm, and downstream channel width 1 cm., The Japan Society of Mechanical Engineers, English

溝部を有するチャネル内流れの伝熱・流れ解析
氏家隆, 黒田明慈, 日本伝熱シンポジウム講演論文集(CD-ROM), 48th, ROMBUNNO.SP204, 2011
Japanese

壁面に衝突する液滴挙動の解析
屋敷俊輔, 黒田明慈, 日本機械学会北海道支部講演会講演概要集, 49th, 65, 66, 07 Nov. 2010
Japanese

溝部を有するチャネル内流れの伝熱・流れ解析
氏家隆, 杉山清英, 黒田明慈, 日本機械学会北海道支部講演会講演概要集, 49th, 69, 70, 07 Nov. 2010
Japanese

308 Simulation of droplet behavior that collides with solid surface
YASHIKI Shunsuke, KURODA Akiyoshi, 北海道支部講演会講演概要集, 2010, 49, 65, 66, 07 Nov. 2010
The Japan Society of Mechanical Engineers, Japanese

310 Numerical Analysis of Heat Transfer and Flow in a Channel with Cavity Portion
UJIIE Takashi, SUGIYAMA Ciyohide, KURODA Akiyoshi, 北海道支部講演会講演概要集, 2010, 49, 69, 70, 07 Nov. 2010
The Japan Society of Mechanical Engineers, Japanese

7・15 流体計測(PIV,超音波,可視化ほか)(7.流体工学,<特集>機械工学年鑑)
黒田 明慈, 日本機械学會誌, 113, 1101, 05 Aug. 2010
一般社団法人日本機械学会, Japanese

Report on the 47th National Heat Transfer Symposium of Japan
CHIKAHISA Takemi, OSONE Yasuo, KURODA Akiyoshi, KUWAHARA Fujio, SAKASHITA Hiroto, TOTANI Tsuyoshi, NAKAMURA Yuji, YAMADA Masahiko, TABE Yutaka, Journal of the Heat Transfar Society of Japan, 49, 208, 19, 28, 01 Jul. 2010
日本伝熱学会, Japanese

液滴衝突により生ずる壁部材応力・ひずみ解析
南貴士, 黒田明慈, 坂健太郎, 佐々木克彦, 日本材料学会学術講演会講演論文集, 59th, 453, 454, 21 May 2010
Japanese

716 Analysis of stress and strain in the solid wall caused by liquid droplet impingement
MINAMI Takashi, KURODA Akiyoshi, SAKA Kentaro, SASAKI Katsuhiko, 学術講演会講演論文集, 59, 0, 453, 454, 21 May 2010
The Society of Materials Science, Japan, Japanese

Effect of separator rib surface pressure on the profile of effective pore radius in gas diffusion layer of PEFC
NAKAGAWA HIROSHI, KUDO KAZUHIKO, KURODA AKIYOSHI, SHIRAISHI RYOTARO, 日本伝熱シンポジウム講演論文集(CD-ROM), 46th, ROMBUNNO.B2-213, 2009
Japanese

Numerical analysis of channel flow with a groove in spanwise direction
OSHIMA HIROFUMI, KURODA AKIYOSHI, 日本伝熱シンポジウム講演論文集(CD-ROM), 46th, ROMBUNNO.C2-135, 2009
Japanese

F107 Moisture movement modeling in hydrophilic gas diffusion layer of PEFC
KUDO Kazuhiko, KURODA Akiyoshi, SUZUKI Hayato, SHIBAYA Humihito, National Symposium on Power and Energy Systems, 2008, 13, 253, 254, 18 Jun. 2008
A model is developed to explain the water movement in a hydrophilic gas diffusion layer (GDL) of PEFC. In the model, a fine hydrophilic columnar fiber is set perpendicular to the surface of the catalyst layer covered by water film. The fiber stands in the channel air flow of the PEFC. The water climbs along the fiber surface up to several tens micron meters for fibers with a diameter range between 3 to 30 micron meters. The calculated results of the evaporation rate from a set of parallel fibers simulating GDL with a void fraction of 0.5 are shown to be much higher than the water generation rate at the catalyst layer with a power density of 1A/cm^2., The Japan Society of Mechanical Engineers, Japanese

G132 Modeling of Water Transmission through Hydrophobic Gas Diffusion Layer of PEFC
Kudo Kazuhiko, Kuroda Akiyoshi, Yamaguchi Takashi, Takeoka Shougo, Watanabe Hitoshi, Procee[d]ings of Thermal Engineering Conference, 2007, 0, 237, 238, 23 Nov. 2007
Cathode side gas diffusion layer (GDL) is modeled considering the behavior of water vapor, liquid water and oxygen diffusion. The model is consists of many parallel hydrophobic pores. By using the model, the current density at which water vapor starts to condense at catalyst side GDL is calculated for various values of GDL porosity and channel air humidity. As the results following results are obtained: the increase in the GDL porosity raises the current density at condensation initiation, and the increase in the supply air humidity reduces the current density., The Japan Society of Mechanical Engineers, Japanese

B112 Modeling of water transmission in hydrophobic gas diffusion layer of PEFC
Kudo Kazuhiko, Kuroda Akiyoshi, Takeoka Shougo, Shimazu Yosuke, Procee[d]ings of Thermal Engineering Conference, 2006, 0, 39, 40, 23 Nov. 2006
In the present study, cathode side GDL of PEFC is modeled as a flat plate with many straight holes with different diameters. Using the model, the mechanism of flooding of PEFC is considered. In the study, water transmission and the oxygen diffusion through the holes are considered. As the generation volume of water in PEFC is very small compared with the volume necessary to overcome the pressure required for the water inflow through small conduits, small conduits are free from water inflow. Therefore, no flooding phenomenon occurs in GDL. It is thought that the relation between the thicknes..., The Japan Society of Mechanical Engineers, Japanese

2327 Numerical Simulation of Toms effect by Equilibrium Dumbbell Element Model
Kuroda Akiyoshi, Wakazono Masayuki, The proceedings of the JSME annual meeting, 2006, 2, 67, 68, 15 Sep. 2006
Numerical simulation of drag reducing flow by Toms effect is carried out using the equilibrium dumbbell element model proposed by the authors. The drag reduction up to 37% drag reduction rate was reproduced by DNS of 2D channel flow in the previous study. In the present study, new character is added on the model, say, the dumbbell element which simulate a polymer can be cut by the stretching force in the fluid. Simulations of 2D channel flows (Re_□=120-600) are carried out and the drag reduction up to 50% drag reduction rate is reproduced by the modified model., The Japan Society of Mechanical Engineers, Japanese

Status and Prospects of New Energy and Energy Conservation Technologies
KURODA Akiyoshi, Journal of the Japan Society of Mechanical Engineers, 109, 1052, 05 Jul. 2006
The Japan Society of Mechanical Engineers, Japanese

C151 Measurement of Self Water Management Characteristics of Double Layered Gas Diffusion Layer
KUDO Kazuhiko, KURODA Akiyoshi, SHINJI Teiichirou, SHIMAZU Yosuke, CHIKAHISA Takemi, Procee[d]ings of Thermal Engineering Conference, 2005, 0, 123, 124, 02 Nov. 2005
In the present study, a new gas diffusion layer (GDL) with self water management is proposed. It is composed of double layered structure with a hydrophilic layer and a water transpiration layer. This GDL is intended to install outside the cathode catalyst layer. The GDL keeps water needed to humidify solid electrolyte layer by the hydrophilic layer and expels surplus water out of the GDL quickly by the water transpiration layer. In the present report, using simulated layers made of non-conducting hydrophilic inorganic sheet and quick-drying fabrics, the characteristics of the water manageme..., The Japan Society of Mechanical Engineers, Japanese

「スペクトル法による数値計算入門」, 石岡圭一著, 東京大学出版会刊, 2004年11月発行, 232頁, 3,800円+税
黒田 明慈, ながれ : 日本流体力学会誌, 24, 2, 25 Apr. 2005
日本流体力学会, Japanese

Numerical Simulation of Drag Reducing Flow by Toms Effect
KURODA Akiyoshi, SUZUKI Jun, KUDO Kazuhiko, Procee[d]ings of Thermal Engineering Conference, 2004, 0, 207, 208, 10 Nov. 2004
A model to simulate the drag reduction by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct nu..., The Japan Society of Mechanical Engineers, Japanese

Numerical Simulation of Drag Reducing Flow by Polymer Additives Using Equilibrium Dumbbell Element Model
KURODA Akiyoshi, SUZUKI Jun, KUDO Kazuhiko, The proceedings of the JSME annual meeting, 2004, 2, 187, 188, 04 Sep. 2004
A model to simulate the drag reduction by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct nu..., The Japan Society of Mechanical Engineers, Japanese

E221 On the mechanism of drag reduction by Toms effect
KURODA Akiyoshi, SUZUKI Jun, KUDO Kazuhiko, Proceedings, ... meeting of Japan Society of Fluid Mechanics, 2004, 0, 382, 383, 09 Aug. 2004
A model to simulate the drag reduction by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct nu..., Japan Society of Fluid Mechanics, Japanese

Study on Super Cooling of Slurry Containing Phase Change Material
KUDO Kazuhiko, NAKATA Katsuhiro, KURODA Akiyoshi, OGUMA Masahito, Thermal science and engineering, 12, 4, 53, 54, 01 Jul. 2004
English

On the Mechanism of Drag Reduction by Toms Effect
KURODA Akiyoshi, SUZUKI Jun, KUDO Kazuhiko, Thermal science and engineering, 12, 4, 9, 10, 01 Jul. 2004
English

大学研究室めぐり(117)北海道大学大学院工学研究科機械科学専攻宇宙環境工学講座 宇宙熱物理工学研究室
工藤 一彦, 黒田 明慈, 持田 あけの, 工業加熱, 41, 4, 87, 92, Jul. 2004
日本工業炉協会, Japanese

On the mechanism of Toms effect based on a discrete element model
Kuroda Akiyoshi, Suzuki Jun, Kudo Kazuhiko, 日本機械学会関東支部総会講演会講演論文集, 2004, 10, 339, 340, 03 Mar. 2004
A model to simulate the drag reductoin by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct nu..., The Japan Society of Mechanical Engineers, Japanese

Mechanism of Drag Reduction by Addition of Dumbbell-like Small Elements in Turbulent Channel Flow
Akiyoshi Kuroda, Shuhei Saido, Kazuhiko Kudo, Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70, 690, 303, 310, 2004
To investigate the mechanism of drag reduction by addition of small elements in turbulent flows of Newtonian fluid, a direct numerical simulation (DNS) of turbulent channel flow has been carried out. Three types of element model (single sphere, rigid dumbbell (two beads are connected by a rigid rod), viscoelastic dumbbell (two beads are connected by a spring and a dashpot)) are used to know the essential function of the small element to reduce the drag in turbulent channel flow. The DNS results with dumbbell models show the drag reduction, while the drag increases with the single sphere model. The effects of parameters including spring constant, damping coefficient, length of the element on the flow features are investigated. In addition the mechanism of the stress deficit by the elements is discussed. Finally, it is shown the primary mechanism of drag reduction by a dumbbell element is to suppress the vortex stretching in the streamwise direction., Japan Society of Mechanical Engineers, Japanese

A modelling of Toms effect based on the discrete element model
Akiyoshi Kuroda, Kazuhiko Kudo, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 70, 698, 2531, 2537, 2004
A model to simulate the drag reductoin by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct numerical simulations are carried out with this new model using the rigid dumbbell element as a discrete element model and it is shown that the drag reduction up to 37% drag reduction rate is reproduced. In addition the followings are indicated as concluding remarks. (1) The drag reduction can be reproduced without assuming the macrostructures formed as the network of elongated polymers or rod-like micelles. (2) The drag reduction and the stress deficit can be reproduced without the elasticity., Japan Society of Mechanical Engineers, Japanese

Numerical Simulation of temperature field in drag reducing flow with dumbbell elements
Kuroda Akiyoshi, Saido Shuhei, Kudo Kazuhiko, Procee[d]ings of Thermal Engineering Conference, 2003, 0, 425, 426, 10 Nov. 2003
A model to simulate the drag reductoin by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct nu..., The Japan Society of Mechanical Engineers, Japanese

Numerical Simulation of Drag Reduction by Microelements Added in a Turbulent Channel Flow
Kuroda Akiyoshi, Saido Shuhei, Kudo Kazuhiko, Fluids engineering conference ..., 2003, 0, 129, 129, 18 Sep. 2003
The Japan Society of Mechanical Engineers, Japanese

A Modeling of Toms Effect based on a Discrete Element Model
KUORDA Akiyoshi, SAIDO Shuhei, Proceedings, ... meeting of Japan Society of Fluid Mechanics, 2003, 0, 446, 447, 28 Jul. 2003
A model of Toms effect is proposed based on a discrete element model. The advantage of the calculation using a discrete model to the calculation using a constitutive equation is that the interaction between the element (polymer) and the medium fluid is directly treated and it is helpful to know the mechanism of the phenomenon. The scale of the discrete model, however, is usually much larger than that of the real polymer because of the restriction of the grid resolution for the flow simulation. The scale of the model should be nearly the same order of that of the turbulent fluctuation. So th..., Japan Society of Fluid Mechanics, Japanese

TED-AJ03-270 NUMERICAL ANALYSIS OF SURFACE TENSION DRIVEN CONVECTION IN A LIQUID DROPLET USING A SPECTRAL METHOD :
KURODA Akiyoshi, TOTANI Tsuyoshi, KUDO Kazuhiko, Proceedings of the ... ASME/JSME Thermal Engineering Joint Conference, 2003, 6, 376, 376, 2003
A three-dimensional numerical analysis is performed to study the Marangoni convection in a spherical liquid droplet cooled uniformly from its surroundings. Like the Benard cells observed on flat liquid surfaces cooled from the surface, the convection occurs even for curved liquid surfaces under appropriate conditions. The essential physical features of the phenomenon come from the fact that surface tension is a monotonous decreasing function of temperature in most fluids. Consider a hot liquid droplet cooling from its surface. When the free surface of a fluid layer is not under a uniform temperature, surface traction from the hot areas to cold areas causes a motion within the fluid. At the hot spot on the surface, warm fluid is drawn towards the surface from the inside of the droplet, which keeps the spot being hot. And this hot fluid spreads across the surface, cooling as it goes. The decrease in temperature across the surface is accompanied by an increase in surface tension that tends to maintain the convection. This phenomenon of the surface-tension-driven convection may affect the heat and mass transport within a small droplet in spray combustion or spray drying. And it may also play an important roll within a droplet under micro-gravity condition, a droplet radiator for example, which may be used as a compact heat-releasing device for space stations. In out study, a method is developed to analyze the three-dimensional transient Marangoni convection in a spherical liquid droplet that is cooled uniformly from its surroundings. As the field is unstable and is very sensitive to the temperature gradients along the surface, it is required for the numerical scheme to be highly accurate and be free from the effects of the polar and central singularities. For the purpose, a spherical harmonic spectral method was adopted to analyze the flow and temperature fields in the droplet on the spherical coordinates. And the transports equation of rƒ (r : radius coordinate, ƒ : velocity components, pressure, temperature) is numerically solved to avoid the singularity at the center of the droplet. The validity of the numerical method is checked at first. And some calculations are carried out to study the effects of parameters, i.e., Marangoni number, Prandt1 number, on the numerical results and it is found that the net heat transport rate within the droplet is affected by the surface tension driven convection when Ma>1000.[figure], 日本機械学会, English

Experimental study on heat and fluid flow in LNG tank heated from the bottom and the side walls
Takuya Kanazawa, Kazuhiko Kudo, Akiyoshi Kuroda, Nobuhiko Tsui, Nippon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 69, 682, 1488, 1494, 2003
Heat and fluid flow in a layer heated from the bottom and the side walls simulating underground LNG tank is experimentally studied under high Rayleigh number (7.5×1010 <
Ra <
1.5×1013) conditions by electrochemical mass transfer technique. From the experiment, following results are obtained. When side walls are heated, the heat transfer along the bottom surface is reduced. Heat transfer along sidewalls is independent of bottom heating, and is modeled by an equation for laminar natural convection flow even for Ra >
109. And convective flow pattern in the tank is visualized by Schlieren technique. The results, combined with local mass transfer measurement, show that Sh is reduced in the area of the bottom surface impinging downward flow. It is caused by the suppression of plume formation by the downward flow., Japan Society of Mechanical Engineers, Japanese

Measurement of Heat Transfer Characteristics and Visualization of Combined Forced and Natural Convection Flow
NOGUCHI Toru, KUDO Kazuhiko, KURODA Akiyoshi, TSUI Nobuhiko, Proceedings of thermal engineering conference, 2002, 0, 199, 200, 06 Nov. 2002
Heat transfer characteristics at the bottom of LNG tank When LNG is injected into a tank is simulated by combined forced and natural convection flow from horizontal heated flat plate. The experiment measured heat transfer coefficient in natural convection dominant region, combined convection region and forced convection dominant region in horizontal heated flat plate. From this, heat transfer characteristics of all of convection region is shown., The Japan Society of Mechanical Engineers, Japanese

Modeling experiment of flow and heat transfer in LNG tank by electrochemical method
KUDO Kazuhiko, KANAZAWA Takuya, KURODA Akiyoshi, TSUI Nobuhiko, Proceedings of thermal engineering conference, 2002, 0, 209, 210, 06 Nov. 2002
Heat and fluid flow in a horizontal layer is experimentally studied high Rayleigh number conditions by electrochemical mass transfer technique. The experiment simulates a LNG tank heated from the bottom and the sidewalls and cooled from the top surface. From the experiment, following results are obtained. When sidewalls are heated, the heat transfer along the bottom surface is reduced. Heat transfer along sidewalls is independent of bottom heating, and is modeled by an equation for laminar natural convection flow even for Ra>(10)^9., The Japan Society of Mechanical Engineers, Japanese

Heat Transfer Analysis of High-temperature Circulator for Radiatively Heating Pure Water Used for Semi-conductor Processing
OGAWA Tomohiko, MOCHIDA Akeno, KUDO Kazuhiko, KURODA Akiyoshi, KADOTANI Kanichi, Proceedings of thermal engineering conference, 2002, 0, 279, 280, 06 Nov. 2002
Heat transfer is analyzed in a radiatively heated pure water circulator. A halogen lamp is inserted along the axis of a cylindrical water passage made of quartz glass. The water and the lamp are separated also by quartz glass wall. To calculate the radiant heat absorbed by the water and the glass, spectral absorption coefficients of them are considered. To carry out non-gray radiative heat transfer analysis, whole spectral range is divided into 10 or 50 bands in the present study. By comparing the calculated results of the radiant heat absorbed by the water and the glass for sub-ranges divi..., The Japan Society of Mechanical Engineers, Japanese

流体科学 : 機械工学年鑑(2000年)
豊田 国昭, 早川 道雄, 坂本 弘志, 松村 昌典, 白濱 芳朗, 新井 隆景, 溝端 一秀, 矢野 猛, 藤川 重雄, 冨田 幸雄, 石川 仁, 望月 修, 高橋 洋志, 河合 秀樹, 粥川 尚之, 羽二生 博之, 一條 眞古人, 黒田 明慈, 矢野 猛, 藤原 満, 風間 俊治, 保里 忠孝, 中村 秀樹, 石毛 秀明, 河田 真広, 若菜 英次, 松本 宏, 日本機械学會論文集. B編, 67, 660, 1870, 1880, 25 Aug. 2001
一般社団法人日本機械学会, Japanese

Study on small-scale co-generation system for domestic house considering partial load and load fluctuation
Shin'Ya Obara, Kazuhiko Kudo, Akiyoshi Kuroda, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 67, 655, 817, 825, 2001
A prototype co-generation system for domestic houses is constructed, and cost reduction and energy saving of the system are studied. The system is constructed to use electricity either from utility or generated by the co-generation system. One of those two electric sources is selected by changeover switch according to cost-minimum control. In addition, by converting optimum amount of generated electricity to heat using an electric heater, the working point of the engine of the co-generation system is tried to be shifted to the highest efficiency condition. New control algorithm is developed to select optimum conversion rate of electricity to heat by electric heater when time-dependent demand of electricity and heat is given. Effects of load fluctuation on the operating cost is also studied. Annual energy cost is calculated to be decreased by 30 per-cent by the system., Japan Society of Mechanical Engineers, Japanese

521 Structure of Temperature Field in Wall-Bounded Flow under an Active Turbulence Control
TSUCHIDA Hiroyuki, KURODA Akiyoshi, KUDO Kazuhiko, 北海道支部講演会講演概要集, 2000, 40, 222, 223, 25 Sep. 2000
A direct numerical simulation of the fully developed velocity and temperature fields in a turbulent channel flow was carried out. We applied a turbulence control to reduce the drag by blowing and suction on the channel walls. In such a flow, it is expected that the similarity between velocity and temperature fluctuations breaks down owing to the local pressure gradient near the blowing region. The unsteady behaviors of coherent structure in the channel flow under the active turbulence control were visualized and animated in this study., The Japan Society of Mechanical Engineers, Japanese

522 Modelling of Combined Forced-and Natural-Convection Heat Trasfer along Bottom Surface of LNG Tank
KUDO Kazuhiko, KURODA Akiyoshi, UCHIYAMA Yasuhisa, TSUI Nobuhiko, 北海道支部講演会講演概要集, 2000, 40, 224, 225, 25 Sep. 2000
Combined forced and natural convection heat transfer from upward-faceing horizontal heated flat plate is nodeled by phenomenological method modifying natural convection heat transfer model at high layer. In this model, mixed or pure natural convection heat transfer coefficient is estimated as averaged one. In the model new boundary layer is assumed to start its growth from a position that previous layer finishes by releasing hot fluid plume "Thermal", and vanishes again at a point where a certain critical condition is satisfied. This theory can explain the transitional phenomena from pure f..., The Japan Society of Mechanical Engineers, Japanese

The Numerical Analysis of Surface Tension Driven Convection in a Liquid Droplet Using a Spectral Method
KURODA Akiyoshi, TSUDA Yuichiro, KUDO Kazuhiko, Fluids engineering conference ..., 2000, 0, 49, 49, 08 Sep. 2000
The Japan Society of Mechanical Engineers, Japanese

Analysis on temperature field in wall-bounded flow-under an active turbulence control for drag reduction
Akiyoshi Kuroda, Takayuki Hirose, Kazuhiko Kudo, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 66, 649, 2413, 2419, 2000
Numerical simulations of the velocity and temperature fields in a fully developed turbulent channel flow were carried out. It is well known that the similarity between the heat transfer and the friction exists in such a turbulent wall bounded flow as the Reynolds analogy. We applied a turbulence control to reduce the drag reduction by blowing and suction on the channel walls. And it is found that the heat transfer rate reduces as well as the skin friction does. But the rate of the heat transfer to the momentum transfer 2SI/Cf is a little larger than that of the natural (no-control) flow. The correlation between velocity and temperature fluctuations weakens owing to the local pressure gradient when the blowing velocity is imposed on the wall against the fluid moving toward the wall (sweep)., Japan Society of Mechanical Engineers, Japanese

Development of estimation method of profiles of equivalent absorption coefficient for gray analysis giving similar results with non-gray analysis
Kazuhiko Kudo, Akiyoshi Kuroda, Tsuyoshi Fujikane, Masahito Oguma, Tsuneaki Nakamura, Nihon Kikai Gakkai Ronbunshu, B Hen/Transactions of the Japan Society of Mechanical Engineers, Part B, 66, 651, 2984, 2991, 2000
Using inverse radiative property value analysis, profiles of gray equivalent absorption coefficient are estimated which give results similar to the ones of nongray analysis when the coefficients are used in the corresponding gary analysis. For the inverse analysis, the results of nongray analysis are used as the input. A new approximate method is proposed for the estimation of the profiles of equivalent absorption coefficient without knowing the results of nongray analysis previously. The profiles of the equivalent absorption coefficient obtained by the new method is compared with the ones estimated by the inverse analysis for six practical cases. And the new method is shown to be useful for estimating the profile of absorption coefficient for gray analysis in most cases., Japan Society of Mechanical Engineers, Japanese

Development of Fast Algorithm for Radiative Heat Transfer in Non-Gray-Gas Systems Surrounded by Gray Walls
KUDE Kazuhiko, KURODA Akiyoshi, OBARA Shin'ya, ISHIBASHI Shin'ya, NAKAMURA Tsuneaki, Transactions of the Japan Society of Mechanical Engineers. B, 65, 630, 741, 748, 25 Feb. 1999
A fast algorithm is developed to solve radiative heat transfer problems is non-gray gas system surrounded by gray walls. In the problem, the distribution of the gas temperature and the wall heat flux in non-gray gas are estimated. In the present study, the time consuming Monte Carlo method is used only outside the iterational loop of the temperature convergence. For the purpose, the R_d values, the ratio of the radiative energy absorbed by an element to the energy emitted from a source element, are separated into two parts, the absorption-coefficient-dependent part and independent part. The..., The Japan Society of Mechanical Engineers, Japanese

Three-Dimensional Numerical Analysis on Transient Marangoni Convection in a Liquid Droplet Using Spherical Harmonic Spectral Method
TOTANI Tsuyoshi, KURODA Akiyoshi, KUDO Kazuhiko, Transactions of the Japan Society of Mechanical Engineers. B, 65, 629, 267, 274, 25 Jan. 1999
A method is developed to analyze the three-dimensional transient Marangoni convection in a liquid droplet heated by a concentric warm rigid sphere set in the center and cooled uniformly from its surroundings. As the system is unstable and the convection is very sensitive to the temperature gradients along the surface, it is required for the scheme to be highly accurate and be free from the effects of the polar singularities. For the purpose, a spherical harmonic spectral method is developed to analyze the flow and temperature fields in the droplet on the three-dimensional spherical coordina..., The Japan Society of Mechanical Engineers, Japanese

Analysis on Three-Dimensional Inverse Load Problem on Radiation Heat Transfer
KUDO Kazuhiko, KURODA Akiyoshi, UCHIDA Hiroshi, OGUMA Masahito, Transactions of the Japan Society of Mechanical Engineers. B, 64, 628, 4102, 4108, 25 Dec. 1998
A method is developed to solve 3-dimensional inverse load problem on radiation heat trasfer. In the present study, the heat flux and temperature distributions of many heater elements arranged along inside a rectangular furnace walls are shown to be estimated from the boundary conditions assigned to the heated objects in the furnace by using the newly developed solution method using singular value decomposition (SVD) technique. The statistical error contained in READ values that represent the radiative heat exchange between elements in the system and are calculated by using the Monte Carlo m..., The Japan Society of Mechanical Engineers, Japanese

Solution Method of Inverse Problems to estimate the Profile of Absorption Coefficient in Two-dimensional Radiative Heat Transfer Systems
KUDO Kazuhiko, KURODA Akiyoshi, OZAKI Eiji, FUJIKANE Tsuyoshi, OGUMA Masahito, Transactions of the Japan Society of Mechanical Engineers. B, 63, 615, 3729, 3736, 25 Nov. 1997
A method to solve inverse radiative property value problems is developed to obtain two-dimensional distribution of absorption coefficient in combustion chambers or furnaces from the profiles of the temperature and the radiative flux of the surrounding walls and of the gas temperature. In the analysis, initial guess of the absorption coefficients of each gas element are given at first, and by solving the forward problem, the wall radiative flux distribution corresponding to the given wall and gas temperature distributions is obtained. The initial guess of the absorption coefficients is corre..., The Japan Society of Mechanical Engineers, Japanese

グラスウール断熱材の有効熱伝導率の解析
李 炳煕, 工藤 一彦, 黒田 明慈, 空気調和・衛生工学, 71, 8, 05 Aug. 1997
Japanese

Spectral Effect of Incident Radiation on Effective Thermal Conductivity of Fibrous Layer due to Radiation
LI Bingxi, KUDO Kazuhiko, KURODA Akiyoshi, Transactions of the Japan Society of Mechanical Engineers. B, 63, 611, 2459, 2465, 25 Jul. 1997
Several models to estimate the effective thermal conductivity of fibrous layers for radiative heat transfer are compared with these calculated using the Monte Carlo method. The models assuming isotropic scattering are shown to underestimate the effective thermal conductivity, and the model based on the two flux model assuming the Milne Eddington approximation is demonstrated to agree very well with the results obtained using the Monte Carlo method. When the incident radiation to the glass fiber layers has spectral variation, the estimated thermal conductivity obtained assuming that the inci..., The Japan Society of Mechanical Engineers, Japanese

Analysis on Effective Thermal Conductivity of Glass Wool Insulations
LI Bingxi, KUDO Kazuhiko, KURODA Akiyoshi, Transactions of the Society of Heating,Air-Conditioning and Sanitary Engineers of Japan., 0, 65, 7, 13, 25 Apr. 1997
This paper presented an analytical method to obtain effective thermal conductivity of glass wool insulation. In the analysis, two dominant modes of heat transfer are considered; heat conduction through gas and fibrous layer and thermal radiation. The analysis was carried out by the two-flux method utilizing the characteristic property values of the layer which are obtained by the Monte Carlo method and are presented in graphical forms as functions of temperature. Even at temperature 0℃, the thermal radiation is shown to share considerable percentage, so, the exact estimation of the radiativ..., The Society of Heating, Air-Conditioning Sanitary Engineers of Japan, Japanese

Solution of the Inverse Radiative Load Problem Using the Singular Value Decomposition Technique
KUDO Kazuhiko, KURODA Akiyoshi, EID Amr, SAITO Tatuhiko, OGUMA Masahito, JSME International Journal Ser. B Fluids and Thermal Engineering, 39, 4, 808, 814, 01 Nov. 1996
A method is developed for solving inverse radiative load problems within multidimensional systems with arbitrary shapes. The energy equations for each gas and wall element are expressed in a matrix form, and the inverse matrix is obtained by the singular value decomposition techniqe in order to estimate the temperature and heat load distributions within the gas region from the profiles of the heat flux and the temperature of the wall elements. From these analyses, the method is shown to give stable results for the radiative inverse load problems when the condition number of the matrix is reduced to an appropriate low value by setting some singular values to 0., The Japan Society of Mechanical Engineers, English

Application of a Method for Solving Inverse Radiative Load Problems to Design of Furnaces
KUDO Kazuhiko, KURODA Akiyoshi, SAITO Tatsuhiko, OGUMA Masahito, Transactions of the Japan Society of Mechanical Engineers. B, 62, 600, 3131, 3136, 25 Aug. 1996
In the present study, the heat Flux and temperature distribution of heating elements surrounding a furnace are estimated by using the singular value decomposition (SVD) method by giving the temperature and heat flux along the surface of a heated object in the furnace. The heat flux profile of the heating elements which satisfies the given condition is obtained by determining the rank of the singular-value matrix using L-curve method., The Japan Society of Mechanical Engineers, Japanese

Numerical Analysis of Radiative Energy Transmission through a Fibrous Layer and Its Experimental Verification : Large-Size-Parameter Case
LI Bingxi, KUDO Kazuhiko, KURODA Akiyoshi, Transactions of the Japan Society of Mechanical Engineers. B, 62, 599, 2840, 2846, 25 Jul. 1996
An analytical model developed to calculate the radiative energy transmission through a fibrous layer is verified by the experimental results obtained via measurement of the transmittance of a He-Ne laser beam through nickel-fiber sheets with a large size parameter. The model is used to calculate the radiative energy transmission by the Monte Carlo method and the optical characteristics of a fiber with large size parameter are estimated by the method developed by Yamada et al. Which considers the diffraction and reflection by the fiber. The following results are obtained. The results of the ..., The Japan Society of Mechanical Engineers, Japanese

Analytical Model of Radiative Heat Transfer through Fibrous Layer
LI Bingxi, KUDO Kazuhiko, KURODA Akiyoshi, Transactions of the Japan Society of Mechanical Engineers. B, 62, 594, 748, 755, 25 Feb. 1996
An analytical model is developed to calculate the radiative heat transfer through a fibrous layer with various fiber orientations consdering the effect of the diameter and the optical properties of the fiber. Milne-Eddington approximation is adopted to obtain a two-flux model type of formulation. To facilitate determination of the extinction efficiency, scattering albedo of the fibrous layer and backscatter factor required for the analysis, these values are shown graphically as the functions of complex index of refraction, size parameter and fiber orientation. The validity of the present mo..., The Japan Society of Mechanical Engineers, Japanese

Effect of Support Rod on Surface-Tension Driven Convection within a Droplet
KUDO Kazuhiko, KURODA Akiyoshi, TANAKA Tatsuru, YANG Wen-Jei, Transactions of the Japan Society of Mechanical Engineers. B, 62, 594, 763, 769, 25 Feb. 1996
The Marangoni convection in a supported liquid droplet suddenly subjected to radiative heating by a hot environment is analyzed by two-dimensional numerical analysis. The effects of the thermal conductivity and the heat capacity of the support rod on the flow and temperature rise within the droplet were studied. The following results are obtained. (1) The surface-tension-driven convection occurs because of the difference between the temperature rise of the surfacees of the support rod and the liquid droplet. (2) The Marangoni convection within the liquid droplet decreases when the heat capa..., The Japan Society of Mechanical Engineers, Japanese

Observations of Turbulence Structure in a Two Dimensional Channel Flow Reproduced by a Direct Numerical Simulation
Kuroda Akiyoshi, Kudo Kazuhiko, Taniguchi Hiroshi, Hasegawa Satoshi, Kanke Jun'ichi, Transactions of the Japan Society of Mechanical Engineers. B, 61, 589, 3137, 3144, 25 Sep. 1995
Recent computer development has enabled such a numerical simulation of turbulence as the direct numerical simulation (DNS). Direct numerical simulation provides valuable information of the flow field, such as the distributions of fluctuating velocity, pressure, and vorticity in the three dimensional space, which are difficult or often impossible to be obtained from experiments. In this study, the unsteady behavior of coherent structures in the two dimensional turbulent channel flow reproduced by a direct numerical simulation was visualized and animated with the aid of three dimensional comp..., The Japan Society of Mechanical Engineers, Japanese

Analysis of Combined Radiative-Convective Heat Transfer in Nongray Gas Jet
Kudo Kazuhiko, Kuroda Akiyoshi, Taniguchi Hiroshi, Otaka Maromu, Ushijima Tetsuhiro, Obata Masakazu, Transactions of the Japan Society of Mechanical Engineers. B, 61, 586, 2235, 2240, 25 Jun. 1995
Combined radiative-convective heat transfer is analyzed in a two-dimensional coaxial jet of nongray gas. The Monte Carlo method is used for the radiative heat transfer analysis. In addition to the nongray analysis, the analysis based on the conventional gray gas assumption is also carried out. From these studies, the gray analysis is found to give higher jet temperature at the nozzle-outlet region and lower temperature at the down-flow region compared with the nongray analysis. The effects of the temperature, velocity, absorbing gas concentration of efflux gas, and the nozzle diameter are a..., The Japan Society of Mechanical Engineers, Japanese

Solution of the Inverse Radiative Load Problem Using the Singular Value Decomposition Technique
Kudo Kazuhiko, Kuroda Akiyoshi, Eid Arm, Saito Tatsuhiko, Oguma Masahito, Transactions of the Japan Society of Mechanical Engineers. B, 61, 585, 1768, 1774, 25 May 1995
A method is developed to solve inverse radiative load problems within multi-dimensional systems with arbitrary shapes. The energy equations for each gas and wall element are expressed in a matrix form, and the inverse matrix is obtained by the singular value decomposition method to estimate the temperature and heat load distributions within the gas region from the profiles of the heat flux and the temperature of the wall elements. From these analyses, the method is shown to give stable results for the radiative inverse load problems when the condition number of the matrix is reduced to an a..., The Japan Society of Mechanical Engineers, Japanese

Analysis of Radiative Energy Transmittance through Ni Fibrous Layer
Kudo Kazuhiko, Taniguchi Hiroshi, Kuroda Akiyoshi, Li Bingxi, Oguma Masahito, Transactions of the Japan Society of Mechanical Engineers. B, 61, 582, 679, 685, 25 Feb. 1995
A method to analyze the radiative energy transmittance through a nickel fibrous layer is developed by using the Monte Carlo method. The validity of the method is shown by comparing the results with the experimental ones obtained by Tong et al. It is also shown that the present analytical method gives more precise results than the two-flux method used by Tong et al. By using the mothod, it is shown that the angular profile of the radiative energy emitted from a black wall which obeys the cosine law is changed into a profile with strong forward transfer. By increasing the size parameter or de..., The Japan Society of Mechanical Engineers, Japanese

Analysis on radiative energy transfer through fibrous layer considering fibrous orientation　　　　　　　　　　　　　　　
Kazuhiko Kudo, Bing Xi Li, Akiyoshi Kuroda, American Society of Mechanical Engineers, Heat Transfer Division, (Publication) HTD, 315, 13, 1995
By using the Monte Carlo method, radiative energy transfer through fibrous layer is analyzed. For the material of the layer, glass and nickel fibers are assumed. Mie scattering is assumed for the scattering mechanism by the fibers. The validity of these method is shown by comparing the results with the experiment obtained by Tong et al.. The heat fluxes through the layer for various temperature differences over the layer and for different thicknesses are predicted well by the method. In the present study, the directional profiles of the scattered radiative energy are obtained to study the effect of multiple-scattering. Two types of fiber orientations are considered: a three-dimensionally randomly oriented layer, and a layer which is oriented randomly in two-dimension and is parallel to the bounding surface. From the analysis, following results are obtained. (1) The heat flux through the layer with three-dimensionally randomly oriented fibrous layer is about 1.3 times larger than that with two-dimensionally randomly oriented layer. (2) The directional profile of scattered energy within the layer changes when the number of scattering is increased. (3) The average extinction efficiency for the radiative energy which has the above mentioned directional profile is almost the same for the layers with the two types of orientations. (4) The difference in the directional profile of scattered energy is the main cause to give the difference in the heat flux passes through the layer with different fiber orientations., English, Book review

Application of Tetrahedral Elements for Radiative Heat Transfer in Arbitrary Shaped Domain
Kudo Kazuhiko, Taniguchi Hiroshi, Kuroda Akiyoshi, Eid Amr, Mochida Akeno, Oguma Masato, Transactions of the Japan Society of Mechanical Engineers. B, 60, 578, 3462, 3468, 25 Oct. 1994
A numerical method is developed, using the Monte Carlo method, for radiative heat-transfer analysis within systems with arbitrary shapes. Triangles with arbitrary sizes and shapes are used as the elements for two-dimensional numerical analysis. For three-dimensional analysis, tetrahedra of arbitrary sizes and shapes are used. The gas and the wall are assumed to be gray, and enthalpy transport by convection can be considered simultaneously. The method was proven to give almost the same results with the previously used program with orthogonal mesh division., The Japan Society of Mechanical Engineers, Japanese

Analysis of Transient Surface-Tension-Driven Convection in a Hemispherically Heated Liquid Droplet
Kudo Kazuhiko, Taniguchi Hiroshi, Kuroda Akiyoshi, Yang Wen-Jei, Tanaka Tatsuru, Yasuno Masanori, Transactions of the Japan Society of Mechanical Engineers. B, 60, 573, 1724, 1729, 25 May 1994
Transient Marangoni convection in a liquid droplet suddenly subjected to a parallel radiative heating is analyzed. The effects of the Marangoni number and the Prandtl number with respect to the developments of flow and temperature fields within the droplet are examined. The following results are obtained : (1) The flow pattern in the droplet changes little with the Marangoni number over a wide range (Ma=1〜10^4) ; (2) the dominant mechanism of heat transfer at early stages is conduction, but it is replaced by convection at later stages provided that the Marangoni number is over 100 ; (3) the..., The Japan Society of Mechanical Engineers, Japanese

Parallelization of 3-D Radiative Heat Transfer Analysis in Non-gray Gas
Kudo Kazuhiko, Taniguchi Hiroshi, Kuroda Akiyoshi, Mochida Akeno, Ohtaka Maromu, Yokota Hiroshi, Fujisaki Masahide, Kosaka Shin'ichi, Yamada Takayuki, Transactions of the Japan Society of Mechanical Engineers. B, 59, 567, 3610, 3616, 25 Nov. 1993
A parallel computational method is developed for the Monte Carlo analysis of radiative heat transfer in three-dimensional nongray gas enclosed by gray walls. The highly parallel computer AP1000 is used for the analysis. For the nongray gas, a mixture of water vapor and carbon dioxide is chosen as the absorbing-emitting medium. Three types of parallelization are studied: type (1), event parallelization; type (2), combination of event parallelization and algorithm parallelization, and type (3), memory-saving algorithm of type (2). When 512 cells are used, values of the speed-up ratios of 395,..., The Japan Society of Mechanical Engineers, Japanese

Radiative Characteristics of Nongray Gas Containing Anisotropic Scattering Particles
Kudo Kazuhiko, Taniguchi Hiroshi, Kuroda Akiyoshi, Sumarsono Markus, Fukuchi Takeru, Transactions of the Japan Society of Mechanical Engineers. B, 59, 565, 2640, 2646, 25 Sep. 1993
The Monte Carlo method is applied to study the effects of nongray gas and anisotropic scattering on the temperature profiles of particle-gas mixture between parallel black cold walls. The gas is nongray combustion gas and the particle is assumed to have gray surface and behaves as an absorber, emitter and anisotropic scatterer of radiative energy. The analysis is based on radiative transfer in a medium which is internally heated uniformly. For comparison, analyses with gray gas and with isotropic scattering particles are also carried out. The results obtained show that within the particle n..., The Japan Society of Mechanical Engineers, Japanese

8. 数値流体力学 機械工学年鑑 (1992年) 流体工学)
小河原 加久治, 黒田 明慈, 日本機械学會論文集. B編, 59, 564, 2343, 2344, 25 Aug. 1993
一般社団法人日本機械学会, Japanese

Improvement of Analytical Method on Radiative Heat Transfer in Nongray Media by Monte Carlo Method
Kudo Kazuhiko, Taniguchi Hiroshi, Kuroda Akiyoshi, Obata Masakazu, Otaka Maromu, Yokota Hiroshi, Transactions of the Japan Society of Mechanical Engineers. B, 59, 560, 1265, 1270, 25 Apr. 1993
An acceleration method is developed for radiative heat transfer analysis in nongray media by the Monte Carlo method. Instead of deciding all the parameters of each energy particle used in the Monte Carlo procedure by stochastic method, the wave number assigned to each energy particle is determined by deterministic method in the present study. This change in the Monte Carlo algorithm reduces the computation time to 1/9 of the original time. To reduce the amount of iteration required to converge the temperature profile in a nongray media layer, an acceleration factor is incorporated to determ..., The Japan Society of Mechanical Engineers, Japanese

B-6 各種気体中での非灰色放射解析
谷口 博, 工藤 一彦, 黒田 明慈, 小幡 正一, 大高 円, ガスタービン秋季講演会講演論文集, 3, 111, 117, 10 Aug. 1991
公益社団法人日本ガスタービン学会, Japanese

Performance Analysis of the Two-Component, Two-Phase Stirling Engine by a Two-Space Engine Model
HlRATA Masaru, KASAGI Nobuhide, MATSUNO Yoshihiro, KURODA Akiyoshi, NINOMlYA Nao, Transactions of the Japan Society of Mechanical Engineers. B, 54, 500, 1014, 1023, 25 Apr. 1988
A performance analysis of the two-component, two-phase Stirling engine has been carried out by using a two-space model, which involves the expansion space, the compression space and the two dead spaces, based upon the assumption that the thermodynamic state point of the condensable working fluid remains within the vapor dome throughout the entire cycle. Experimental studies have also been made using two engines which operate under different system-pressure conditions : the first one is a single acting, two-piston, parallel cylinder type engine using teflon bellows as a cylinder and operates..., The Japan Society of Mechanical Engineers, Japanese

Numerical Investigation of the Turbulent Heat Transfer Mechanism Near the Wall by the Unsteady Streamwise Pseudo-Vortical Motion Model
KASAGI Nobuhide, KURODA Akiyoshi, HIRATA Masaru, Transactions of the Japan Society of Mechanical Engineers. B, 53, 490, 1812, 1821, 25 Jun. 1987
The unsteady streamwise pseudo-vortical motion model developed by Kasagi et al. (1985) is used in a numerical analysis of the turbulent heat transfer near the wall for various Prandtl-number fluids under the wall boundary conditions of constant heat flux and constant temperature. Unlike the typical methodology based on Reynolds decomposition, the algebraic expressions of three fiuctuating velocities given by the model are directly introduced into the governing energy equation. From the numerical solution of the unsteady thermal field, the near-wall behavior of statistical quantities is obta..., The Japan Society of Mechanical Engineers, Japanese

医療人のための流体力学 入門 第4回 数式が苦手でもわかる流体力学の基礎から循環器領域への応用まで 流線による流れの可視化・剥離と壁面せん断応力　　　　　　　　　　　　　　　
黒田明慈, 大島伸行, 横山博一
INNERVISION, Aug. 2019, [Joint work]

医療人のための流体力学 入門 第3回 数式が苦手でもわかる流体力学の基礎から循環器領域への応用まで 層流と乱流　　　　　　　　　　　　　　　
大島伸行, 黒田明慈, 横山博一
INNERVISION, Jun. 2019, [Joint work]

エネルギー・環境への考え方―その提言と問いかけ
谷口 博, 毛利 邦彦, 谷口 正行, 黒田 明慈, 三浦 隆利
養賢堂, Mar. 2008, 4842504323, 153, [Joint work]

パソコン活用のモンテカルロ法による放射伝熱解析
谷口 博, 工藤 一彦, 持田 明野, Wen Jei Yang, 黒田 明慈
コロナ社, Dec. 1993, 4339043168, 231, [Joint work]

Modeling of Flooding Mechanism in Gas Diffusion Layer of Fuel Cell
Grants-in-Aid for Scientific Research(基盤研究(B))
2007 - 2008
Kazuhiko KUDO, Akiyoshi KURODA
疎水性ガス拡散層における水分排出モデル開発固体高分子形燃料電池のカソード側ガス拡散層(GDL)を、並列疎水性円管流路で模擬し、GDL内フラディング機構を考察した。またこの解析で使用するGDL内の等価細孔径分布を、実験的に求めた。この結果、水排出流路以外に、これらと連通した独立内部空隙を有するGDLモデルの必要性が示された親水性ガス拡散層における水分排出モデル開発速乾繊維類似の、表面にV 溝を有する親水性繊維1本を水に垂直に立て、強制対流中に置いた場合の、繊維からの水蒸発特性をモデル化した。この結果、このような親水性GDL により電池の生成水分を十分に排出できることが示された。
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 北海道大学, Coinvestigator not use grants, Competitive research funding, 19360093

On the mechanism and prediction of the drag reducing turbulent flow by Toms effect
Grants-in-Aid for Scientific Research(基盤研究(C))
2006 - 2007
Akiyoshi KURODA
The phenomenon of the drag reduction caused by chain polymer molecule or the surfactant which forms the rod-like micelle is known as Toms effect. Our minute discrete element model like dumbbell simulates chain polymer molecule and surfactant. We assumed that the element was in equilibrium for fluctuation of medium and modeled surfactant additive flow. In our previous research(1), we represented the 37% drag reduction can be reconstructed through Direct Numerical Simulation (DNS) of two-dimensional turbulent channel flow. From these results, we consider that the element weakens the longitudi...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 北海道大学, Principal investigator, Competitive research funding, 18560150

Optical Measurement of Solidification Ratio in Phase Change Slurry considering Refraction in Droplets
Grants-in-Aid for Scientific Research(基盤研究(B))
2005 - 2006
Kazuhiko KUDO, 黒田 明慈, 持田 明野
The objective of the present study is to develop an optical method to measure the solidification ratio of paraffin droplets suspended in phase change slurry. For the purpose, an analytical model was developed using the Monte Carlo method. The model calculates the transmittance and reflectance of the phase change slurry layer for laser beam with a wavelength of 670nm. The slurry contains paraffin particles with different diameters and different optical properties Experiments were also carried out to measure the transmittance and reflectance of the phase change slurry layer for laser beam wit...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 北海道大学, Coinvestigator not use grants, Competitive research funding, 17360088

A Modeling of Toms Effect Based on the Discrete Element Model
Grants-in-Aid for Scientific Research(基盤研究(C))
2004 - 2005
Akiyoshi KURODA, 工藤 一彦
A model to simulate the drag reductoin by dilute addition of polymer or surfactant (Toms effect) is proposed based on the discrete element model. The dimension of the discrete element, which represents the polymer or the rod-like micelle, is very small compared to that of the velocity fluctuation of the fluid. So it is assumed that the element is in equilibrium state in the fluid and turns to the direction of an eigenvector of the velocity gradient tensor. And the macroscopic effect of the discrete elements is modeled as the stress assuming the elements are independent each other. Direct nu...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 北海道大学, Principal investigator, Competitive research funding, 16560169

Analysis of drag reduction and heat transfer under a non-similar condition between turbulent flow and temperature fields
Grants-in-Aid for Scientific Research(基盤研究(C))
2001 - 2002
Akiyoshi KURODA, 工藤 一彦
Numerical simulations of the velocity and temperature fields in a fully developed turbulent channel flow were carried out. It is well known that the similarity between the heat transfer and the friction exists in such a turbulent wall bounded flow as the Reynolds analogy. We applied a turbulence control to reduce the drag by blowing and suction on the channel walls. And it is found that the heat transfer rate reduces as well as the skin friction does. But the rate of the heat transfer to the momentum transfer is a littie larger than that of the natural (no-control) flow. The correlation bet...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(C), 北海道大学, Principal investigator, Competitive research funding, 13650205

Estimation of Radiative and Scattering Characteristics of Sodium Aerosols Using Inverse Analysis
Grants-in-Aid for Scientific Research(基盤研究(B))
2001 - 2002
Kazuhiko KUDO, 持田 明野, 黒田 明慈
Estimation method is studied for complex index of refraction of aerosol generated by sodium fire. In the present study, non-gray radiative transfer analysis is carried out to simulate the radiative transmission through uniformly distributed dispersed aerosol layer for given values of complex index of refraction considering multiple scattering. The Monte Carlo method is used for the analysis.Using the program, several sets of contour curves of the transmittance of aerosol layer are obtained at several positions on the wall situated opposite to the black body furnace for a wide range of compl...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 北海道大学, Coinvestigator not use grants, Competitive research funding, 13450079

摩擦低減制御下にある壁面乱流の伝熱特性に関する研究
科学研究費補助金(奨励研究(A))
1998 - 1999
黒田 明慈
本研究は、壁面乱流において壁面からの吹出し・吸い込みによる制御を行った場合に壁面摩擦と熱伝達率の減少に非相似な効果が現れることをシミュレーションによって確認することを目的とし、これを達成するため、壁面に向かう流体運動に対しては吹出しを壁面から離れる流体運動に対しては吸い込みを行う制御を伴った2次元チャネル内乱流および温度場の直接シミュレーションコードを作成し、計算を実行した。計算結果は3次元空間の時系列データとしてCD-RあるいはDVD-ramの大容量記憶媒体に記録し、可視化や種々の数値実験が行えるものとしてデータベース化した。このデータベースを利用した数値実験や可視化の結果、以下の知見を得た。(1)制御を加えることによって壁面摩擦係数C_f、スタントン数ともに20%程度減少した。また、両者の比である2St/C_fは約3%上昇した。(2)相対的に流速の大きい流体塊が壁に向かう運動に対して吹出しを行っている領域では流れ方向速度変動と温度変動の相関係数が大きく低下する。(3)吹出し制御領域では2St/C_fが増加するが、吸込み領域がスパン方向に隣接し、ここで2St/C_fが減少する。この現象は縦渦構造の壁に向かう運動と壁から離れる運動に対応している。(4)2St/C_fが増加する吹出し制御領域では大きな逆圧力勾配が生じており、この圧力勾配の効果によって速度場と温度場の非相似性が現...
文部科学省, 奨励研究(A), 北海道大学, Principal investigator, Competitive research funding, 10750135

Development of Fast Numerical Method to Solve Nongray Radiative Heat Transfer in Three-dimensional Arbitrary Shaped Systems by Pre-calculating Geometrical Characteristics
Grants-in-Aid for Scientific Research(基盤研究(B))
1997 - 1998
Kazuhiko KUDO, 小熊 正人, 中村 恒明, 持田 明野, 黒田 明慈
The objective of this research is to develop a threed-dimensioal nongray radiative-convective heat transfer program for arbitrary shaped systems. For the purpose, new fast algorithm for numerical analysis on nongray radiative heat transfer is developed and confined with a threed-dimensioal nongray radiative-convective heat transfer program for arbitrary shaped systems..In the study, the Monte Carlo method is adopted for the analytical tool for the radiative transfer calculation. As the method is known to be time-consuming, below mentioned unique fast algorithm for numerical analysis on nong...
Ministry of Education, Culture, Sports, Science and Technology, 基盤研究(B), 北海道大学, Coinvestigator not use grants, Competitive research funding, 09555068

乱流素過程のモデリングに関する研究
科学研究費補助金(重点領域研究)
1993 - 1995
笠木 伸英, 長野 靖尚, 島 信行, 木谷 勝, 黒田 明慈, 西野 耕一, 中山 昭彦
本年度は,8名の研究者が,互いに連絡を取りながら,各々が基礎的な乱流の素過程を取り上げ,異なる手法を用いてデータベースの構築,モデル化のための研究を行った.鉛直あるいは水平方向浮力を伴う壁乱流,回転を伴う壁乱流,特殊な境界条件を有する壁乱流のDNSデータベースを構築した.スカラーフラックスの輸送方程式モデルの拡張,修正を行い,ステップ剥離流に対してその評価を行った.(笠木伸英)(2)3次元離散渦法において渦要素の挙動に粘性効果を取り込む方法を総合的に検討し,渦要素の核半径を時間的に成長させるモデルおよび渦粘性のSGSモデルが適切であることを明らかにした.軸対称およびヘリカル撹乱を与えたときの円形噴流における渦構造の発展過程を対象に評価が行われた.(木谷勝)(3)直接数値シミュレーションのデータベースに基いて,レイノルズ応力輸送において最も重要な素過程である再分配のモデリングを行った.開発されたモデルは,複雑境界乱流への適用を阻害する壁面効果項を含まず,かつ底層領域にも適用できるという点で一般性が高い.また,レイノルズ応力に関して準線形であるという点で簡明なものである.(島信行)(4)乱流モデルに非局所と間欠性のモデル化を組み込む提案を行った.具体的には2方程式モデルに空間積分型モデルを乱流応力並びに輸送項に適応し非局所性を表現した.ステップ剥離流,異種剪断流の干渉する複雑乱流...
文部科学省, 重点領域研究, 東京大学, Coinvestigator not use grants, Competitive research funding, 05240103

乱流の直接数値シミュレーションにおける差分法の適用に関する研究
科学研究費補助金(奨励研究(A))
1994 - 1994
黒田 明慈
1.スペクトル法によって再現した二次元チャンネル内乱流場に1次〜6次の差分スキー無を適用し、1階微分値、2階微分値に加え、対流項、拡散項としての精度を系統的に評価した。その結果、以下の知見を得た。(1)差分法による微分値とスペクトル法による微分差は、緩和領域で最大となる。(2)(1)の差を局所の微分値で除した相対差は、チャネル幅にわたってほぼ一定である。(2)拡散項に比べて対流項の誤差はきわめて大きい。(3)1階微分における4次精度中心差分と5次精度風上差分の差はほとんどない。(4)2階微分では、少なくとも6次精度までは、差分の名目上の精度を上げることによって実質的な精度向上が得られる。2.対流項に1次精度風上差分、拡散項に2次精度中心差分を適用し、二次元チャネル内乱流のシミュレーションを行った。その結果、スペクトル法により再現した流れ場を初期条件とした場合に層流化する傾向がみられ、1次精度風上差分のもたらす数値粘性の影響が無視できないことを確認した。
文部科学省, 奨励研究(A), 北海道大学, Principal investigator, Competitive research funding, 06750190

直接数値シミュレーションを用いた乱流構造の非定常挙動に関する研究
科学研究費補助金(奨励研究(A))
1993 - 1993
黒田 明慈
乱流の直接数値シミュレーションの供出するデータを用いて乱流の準秩序構造の非定常挙動を観察することは,乱流構造解析において有効な手段であるにもかかわらず取り扱うデータが極めて膨大となることからその実現には困難が伴う。本研究では,シミュレーションプログラムと可視化プログラムをリンクさせることによりこの問題点を解決して,各種変動物理量の等値面を抽出,可視化しその時系列データを動画として記録するシステムを構築した。さらにこのシステムを利用して,二次元チャネル内乱流中のストリーク構造.渦構造,イジクション・スイ-プの時空間的挙動をDELTAt^+=357にわたって動画として記録した。これらの観察を通じ,乱流構造の発生,発展,消滅の課程に対して検討を加え,以下のような知見を得た。1.渦構造と強い乱流応力の発生領域は,空間的に近接して存在し,これらの領域は空間的に間欠性をもって分布している。このうち運動が活発な領域においては,複数の渦構造が連続的に発生し,活性化された状態は数百nu/u_^2以上にわたって継続する。2.渦構造,イジェクション,スイ-プの内ではイジェクションがもっとも安定して存在し続け,観察時間中において移動・変形を繰り返すが,不活性領域に新たにイジェクションが発生することは,極めてまれである。また,渦構造の発達にともなってイジェクション領域が拡大することはあっても...
文部科学省, 奨励研究(A), 北海道大学, Principal investigator, Competitive research funding, 05750182

大容量直接シミュレーションデータベースによる壁近傍乱流構造の動的挙動に関する研究
科学研究費補助金(重点領域研究)
1993 - 1993
黒田 明慈, 工藤 一彦, 谷口 博
二次元チャネル内乱流の直接数値シミュレーションを行い,これより速度,圧力,乱流応力等の等値面を可視化し,その時空間的挙動を動画として記録するシステムを構築した。本システムでは,場の時間発展を観察する際には、視点を下流方向に一定速度で移動させることにより,着目した構造の変化を長時間にわたって追跡することが可能となっている。本システムを用いてΔt^+=357にわたる動画を作成し,観察した結果以下のような知見を得た。1.渦構造とイジェクション,スイープの発生領域は,空間的に近接して存在し、これらの領域は空間的に間欠性をもって分布している。この運動が活発な(活性化された)領域においては,複数の渦構造が連続的に発生し,活性化された状態が数百ν/u_τ^2以上にわたって継続する。2.渦構造,イジェクション,スイープの内ではイジェクションがもっとも安定して存在し続け,観察時間中において移動・変形を繰り返すが,不活性領域に新たにイジェクションが発生することはまれである。また,渦構造の発達にともなってイジェクション領域が拡大することはあっても,新たに発生することはなく,むしろイジェクション領域の下流部において渦の発生が確認されることが多く観察された。3.渦構造発生時の回転軸方向は流れ方向からスパン方向の広い角度に分布しており,発展時における流れ方向への伸張を経て縦渦の形態をとる。また,乱流構造...
文部科学省, 重点領域研究, 北海道大学, Principal investigator, Competitive research funding, 05240201

液滴内3次元過渡表面張力対流の発達に関する研究(曲率を有する液面でのベナード対流)
科学研究費補助金(一般研究(C))
1993 - 1993
工藤 一彦, 黒田 明慈, 谷口 博
1.球状液滴内2次元非定常表面張力対流解析プログラムによる解析既開発の題記プログラムを用い、外部加熱・冷却条件と、表面張力対流の強さの関係を調べた。また、実用上問題となる液滴全体の平均温度の上昇に及ぼすマランゴニ数の影響について調べた。この結果、マランゴニ数の増加は液滴表面の周方向の温度差は増大させる効果はあるものの、入熱と出熱を共に増加させるため、液滴の平均温度の上昇にはあまり寄与しないことを明らかにした。2.球状液滴内3次元非定常表面張力対流解析プログラムの開発題記表面張力対流の解析のために、3次元球座標系において有限体積法を用いて基礎式の差分化を行い、SIMPLE法で解析を行うプログラムの開発を行った。このプログラムでは、球を半径方向に32、周方向に32、天頂角方向に64に等分割している。初期条件としては球状液滴全体の温度を均一とし、外部の雰囲気温度を時刻>0でステップ状に一様に降下させることで表面張力対流を生起させるものである。ここで、液滴は外部雰囲気との間で一定の対流熱伝達率で熱を奪われるとする。現状では、表面張力対流の開始位置を固定するため、表面上の一点の初期温度として他の部分より10%高い値を与えてある。以上の解析により、現在までに3次元球状液滴中の1個の表面張力対流渦の成長過程が計算された。これによると、従来の平らな液面における表面張力対流では、表面近傍に限定...
文部科学省, 一般研究(C), 北海道大学, Coinvestigator not use grants, Competitive research funding, 05805020

構造論的乱流モデルを用いた壁近傍乱流輸送機構に関する研究
科学研究費助成事業
1988 - 1989
黒田 明慈
日本学術振興会, 奨励研究(A), 東京大学, 63790284