Papers - Kobayashi, Hiromichi

Numerical Study on Entrance Length in Thermal Counterflow of Superfluid ⁴He

Kobayashi H., Yui S., Tsubota M.

Journal of Low Temperature Physics (Journal of Low Temperature Physics)  196 ( 1-2 ) 35 - 41 2019.07

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00222291

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© 2019, Springer Science+Business Media, LLC, part of Springer Nature. Three-dimensional numerical simulations in a square duct were conducted to investigate entrance lengths of normal fluid and superfluid flows in a thermal counterflow of superfluid 4He. The two fluids were coarse-grained by using the Hall–Vinen–Bekharevich–Khalatnikov (HVBK) model and were coupled through mutual friction. We solved the HVBK equations by parameterizing the coefficient of the mutual friction to consider the vortex line density. A uniform mutual friction parameter was assumed in the streamwise direction. Our simulation showed that the entrance length of the normal fluid from a hot end becomes shorter than that of a single normal fluid due to the mutual friction with the parabolically developed superfluid flow near the hot end. As the mutual friction increases, the entrance length decreases. Same as that, the entrance length of the superfluid from a cold end is affected by the strength of the mutual friction due to the parabolically developed normal fluid flow near the cold end. Aside from the entrance effect, the realized condition of a tail-flattened flow is discussed by parameterizing the superfluid turbulent eddy viscosity and the mutual friction.

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格子ボルツマン法による自転車競技の集団走行の大規模LES空力解析

長谷川 雄太，青木 尊之，小林 宏充，白﨑 啓太

日本機械学会論文集 (日本機械学会)  85 ( 870 ) 18-00441 2019.02

Research paper (scientific journal), Joint Work, Accepted

Improvement of the SGS model by using a scale-similarity model based on the analysis of SGS force and SGS energy transfer

Kobayashi H.

International Journal of Heat and Fluid Flow (International Journal of Heat and Fluid Flow)  72   329 - 336 2018.08

Research paper (scientific journal), Single Work, Accepted,  ISSN  0142727X

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© 2018 Elsevier Inc. The subgrid-scale (SGS) model is improved by using a scale-similarity model based on the analysis of the SGS force and SGS energy transfer around an elliptic Burgers vortex. Abe (2013) proposed an anisotropy-resolving SGS model in which the Bardina term of a scale-similarity model is mixed with an eddy viscosity model under a new concept wherein the Bardina term does not affect the SGS energy transfer although it affects the SGS force. By using the concept, we propose a scale-similarity model with the Clark term. The SGS energy transfer is determined by the scale-similarity term and not by the eddy viscosity term while the SGS force is improved by using the SGS kinetic energy (Abe, 2013). It is observed that the Clark term yields higher spatial correlation with the true distributions of the SGS force and SGS energy transfer around the elliptic vortex when compared to the Bardina term. The SGS model based on the Clark term exhibits good performance for turbulent channel flows with respect to Reτ=180 and 590 even in extremely coarse grid resolutions. Specifically, the SGS model with the SGS kinetic energy fairly improves the mean streamwise velocity profile.

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Three-Dimensional Coupled Dynamics of the Two-Fluid Model in Superfluid 4He: Deformed Velocity Profile of Normal Fluid in Thermal Counterflow

Satoshi Yui, Makoto Tsubota, Hiromichi Kobayashi

Physical Review Letters (Physical Review Letters)  120 ( 155301 )  2018.04

Research paper (scientific journal), Joint Work, Accepted,  ISSN  00319007

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© 2018 American Physical Society. The coupled dynamics of the two-fluid model of superfluid He4 is numerically studied for quantum turbulence of the thermal counterflow in a square channel. We combine the vortex filament model of the superfluid and the Navier-Stokes equations of normal fluid. Simulations of the coupled dynamics show that the velocity profile of the normal fluid is deformed significantly by superfluid turbulence as the vortices become dense. This result is consistent with recently performed visualization experiments. We introduce a dimensionless parameter that characterizes the deformation of the velocity profile.

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液体金属MHD発電の最近の進展

小林宏充

日本エネルギー学会機関誌えねるみくす (日本エネルギー学会)  96   193 - 198 2017.03

Research paper (scientific journal), Single Work

Turbulent and Electrical Phenomena in a Liquid Metal MHD Energy Conversion Device under Various Load Conditions

Hiromichi Kobayashi, Yoshihiro Okuno

IEEJ Transactions on Power and Energy 136 ( 10 ) 773 - 778 2016.10

Research paper (scientific journal), Joint Work, Accepted

Analyses on Response of A Liquid Metal MHD Power Generation System to Various External Inputs

Liancheng Hu, Hiromichi Kobayashi, Yoshihiro Okuno

IEEJ Transactions on Electrical and Electronic Engineering 10 ( 3 ) 268 - 273 2015.05

Research paper (scientific journal), Joint Work, Accepted

Cyclone-anticyclone asymmetry in gravity wave radiation from a co-rotating vortex pair in rotating shallow water

Norihiko Sugimoto, Keiichi Ishioka, Hiromichi Kobayashi and Yutaka Shimomura

Journal of Fluid Mechanics (Cambridge University Press)  772   80-106 2015.04

Research paper (scientific journal), Joint Work, Accepted

Influence of Working Fluid Characteristics on the Performance of a Liquid Metal Magnetohydrodynamic Generator

Liancheng Hu, Hiromichi Kobayashi, Yoshihiro Okuno

Electrical Engineering in Japan B 134 ( 12 ) 1-10 2014.12

Research paper (scientific journal), Joint Work, Accepted

Direct Numerical Simulation and Large Eddy Simulation on a Turbulent Wall-Bounded Flow Using Lattice Boltzmann Method and Multiple GPUs

Xian Wang, Yanqin Shangguan, Naoyuki Onodera, Hiromichi Kobayashi, and Takayuki Aoki

Mathematical Problems in Engineering 2014   1-10 2014.04

Research paper (scientific journal), Joint Work, Accepted

A Reynolds-averaged turbulence modeling approach to the maintenance of the Venus superrotation

Akira Yoshizawa, Hiromichi Kobayashi, Norihiko Sugimoto, Nobumitsu Yokoi, Yutaka Shimomura

Geophysical & Astrophysical Fluid Dynamics (Taylor & Francis)  107 ( 6 ) 614-639 2013.08

Research paper (scientific journal), Joint Work, Accepted

大学一年生の自然科学への関心度と知識度2012年度調査 -- 10年前、20年前との比較

加藤万里子，小林宏充，黒田忠広，青木健一郎，杉本憲彦，松浦 壮

慶應義塾大学日吉紀要 (慶應義塾大学出版会)   ( 53 ) 1-22 2013.03

Research paper (bulletin of university, research institution), Joint Work

Turbulent duct flows in a liquid metal magnetohydrodynamic power generator

Hiromichi Kobayashi, Hiroki Shionoya, Yoshihiro Okuno

Journal of Fluid Mechanics (Cambridge University Press)  713   243-270 2012.12

Research paper (scientific journal), Joint Work, Accepted

Large-Eddy Simulation of Turbulent Channel Flows with Conservative IDO Scheme

Naoyuki Onodera, Takayuki Aoki, Hiromichi Kobayashi

Journal of Computational Physics (Elsevier)  230 ( 14 ) 5787-5805 2011.05

Research paper (scientific journal), Joint Work, Accepted

Statistical properties of the local structure of homogeneous isotropic turbulence and turbulent channel flows

Hiromichi Kobayashi, Eiji Matsumoto, Naoya Fukushima, Mamoru Tanahashi, Toshio Miyauchi

Journal of Turbulence (Taylor & Francis)  12 ( 11 ) 1-16 2011.01

Research paper (scientific journal), Joint Work, Accepted

GPUによるラージエディ・シミュレーションの高速化

小野寺直幸，青木尊之，小林宏充

日本流体力学会誌ながれ (日本流体力学会)  29 ( 6 ) 423-426 2010.12

Research paper (scientific journal), Joint Work

木質系バイオマスガス化発電システムの検討

小林 宏充

木質系バイオマスエネルギー利活用研究事業報告書 (はままつ産業創造センター)     79088 2008.07

Research paper (conference, symposium, etc.), Single Work

低磁気レイノルズ数のMHD乱流

小林宏充

日本流体力学会誌ながれ (日本流体力学会)  27 ( 3 ) 217-224 2008.06

Research paper (scientific journal), Single Work

Application of a local SGS model based on coherent structures to complex geometries

Hiromichi Kobayashi, Frank Ham, Xiaohua Wu

International Journal of Heat and Fluid Flow (Elsevier)  29 ( 3 ) 640-653 2008.06

Research paper (scientific journal), Joint Work, Accepted

Large eddy simulation of magnetohydrodynamic turbulent duct flows

Hiromichi Kobayashi

Physics of Fluids (American Institute of Physics)  20 ( 1 ) 015102 2008.01

Research paper (scientific journal), Single Work, Accepted