Details of a Researcher - Kobayashi, Hiromichi

Papers - Kobayashi, Hiromichi

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Quantum Turbulence Coupled with Externally Driven Normal-Fluid Turbulence in Counterflow of Superfluid 4He

Yui S., Kobayashi H., Tsubota M., Yokota R.

Journal of the Physical Society of Japan 94 ( 4 ) 2025.04

ISSN 00319015

The coupled dynamics of quantum turbulence (QT) and normal-fluid turbulence (NFT) have been a central challenge in quantum hydrodynamics. We numerically studied the coupled dynamics of the two turbulences in thermal counterflow. NFT is driven by external forces to control its turbulent intensity, and the fast multipole method accelerates the calculation of QT. We show that NFT enhances QT via mutual friction. The vortex line density L of the QT satisfies the statistical law L1/2 ≈ γVns with the counterflow velocity Vns. It is found that the response coefficient γ is amplified by NFT. We propose a theoretical insight into the relation between the two turbulences.

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Turbulent Taylor-Couette flow with magnetohydrodynamic interaction in axial magnetic field

Kobayashi H., Hasebe T., Fujino T., Takana H.

Physics of Fluids 37 ( 2 ) 2025.02

ISSN 10706631

Turbulent Taylor-Couette flow applied in the axial magnetic field with upper and lower walls is numerically investigated by large-eddy simulation. As the Hartmann number increases proportional to the magnetic field, turbulent fluctuations are suppressed, and the flow is laminarized. The alignment of vortex structures is drastically changed from the azimuthal direction to the axial direction. The fine streaks near the inner wall are suppressed, and the high-speed triplet streaks emerge near the inner wall. The electric current streamlines reveal the feature of the difference between open and short circuit conditions.

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Large-eddy simulation of high-Reynolds-number turbulent channel flow controlled using streamwise travelling wave-like wall deformation for drag reduction

Nabae Y., Inagaki K., Kobayashi H., Gotoda H., Fukagata K.

Journal of Fluid Mechanics 1003 2025.01

ISSN 00221120

We investigate the drag reduction effect of the streamwise travelling wave-like wall deformation in a high-Reynolds-number turbulent channel flow by large-eddy simulation (LES). First, we assess the validity of subgrid-scale models in uncontrolled and controlled flows. For friction Reynolds numbers and, the Smagorinsky and wall-adapting local eddy-viscosity (WALE) models with a damping function can reproduce well the mean velocity profile obtained by direct numerical simulation (DNS) in both the uncontrolled and controlled flows, leading to a small difference in drag reduction rate between LES and DNS. The LES with finer grid resolution can reproduce well the key structures observed in the DNS of the controlled flow. These results show that the high-fidelity LES is valid for appropriately predicting the drag reduction effect. In addition, a small computational domain is sufficient for reproducing the turbulence statistics, key structures and drag reduction rate obtained by DNS. Subsequently, to investigate the trend of drag reduction rate at higher Reynolds numbers, we utilize the WALE model with the damping function to investigate the control effect at higher Reynolds numbers up to. According to the analyses of turbulence statistics and instantaneous flow fields, the drag reduction at higher Reynolds numbers occurs basically through the same mechanism as that at lower Reynolds numbers. In addition, the drag reduction rate obtained by the present LES approaches that predicted using the semi-empirical formula (Nabae et al., Intl J. Heat Fluid Flow, vol. 82, 2020, 108550) as the friction Reynolds number increases, which supports the high predictability of the semi-empirical formula at significantly high Reynolds numbers.

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Influence of different mutual friction models on two-way coupled quantized vortices and normal fluid in superfluid He 4

Kobayashi H., Yui S., Tsubota M.

Physical Review Fluids 9 ( 10 ) 2024.10

We study the influence of two mutual friction models on quantized vortices and normal fluid using two-way coupled simulations of superfluid He4. The normal fluid is affected by quantized vortices via mutual friction. A previous study [Y. Tang, Nat. Commun. 14, 2941 (2023)2041-172310.1038/s41467-023-38787-w] compared the time evolutions of the vortex ring radius and determined that the self-consistent two-way coupled mutual friction (S2W) model yielded better agreement with the experimental results than the two-way coupled mutual friction (2W) model whose model parameters were determined through experiments with rotating superfluid helium. In this study, we compare the two models in more detail in terms of the quantized vortex ring propagation, reconnection, and thermal counterflow. We show that the S2W model exhibits better results than the 2W model on the microscopic scale near a quantized vortex, such as during quantized vortex ring propagation and reconnection, although the S2W model requires a higher spatial resolution. For complex flows such as a thermal counterflow, the 2W model can be applied even to a low-resolution flow while maintaining the anisotropic normal fluid velocity fluctuations. In contrast, the 2W model predicts lower normal fluid velocity fluctuations than the S2W model. The two models show probability density functions with-3 power-law tails for the normal fluid velocity fluctuations.

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Highly Reproducible Synthesis of Hollow Zirconia Particles via Atmospheric-Pressure Plasma Processing with Inkjet Droplets

Nitta K., Sakai T., Muneoka H., Shimizu Y., Kobayashi H., Terashima K., Ito T.

Plasma Chemistry and Plasma Processing (Plasma Chemistry and Plasma Processing) 44 ( 1 ) 289 - 303 2024.01

ISSN 02724324

Hollow particles have attracted considerable attention owing to their unique properties. In this study, hollow monoclinic zirconia particles were directly synthesized from inkjet droplets of a zirconyl hydroxychloride aqueous solution via atmospheric-pressure plasma processing. Hollow structures with craggy surfaces were obtained in the plasma at gas temperatures above 1000 K. The steep solvent evaporation rate induced by the localized high-energy reaction field of the atmospheric-pressure plasma may have induced solute condensation near the droplet surface and contributed to the formation of hollow particles. The average diameter of the synthesized particles was ~ 3 μm, while their size distribution was narrow (coefficient of variation: 0.06–0.10). The high reproducibility of the synthesized particles was attributed to the small variations in inkjet droplet size. The proposed method enables the rapid synthesis of hollow particles of various inorganic materials, while controlling their number and composition.

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Imaging quantized vortex rings in superfluid helium to evaluate quantum dissipation

Tang Y., Guo W., Kobayashi H., Yui S., Tsubota M., Kanai T.

Nature Communications (Nature Communications) 14 ( 1 ) 2023.12

The motion of quantized vortices is responsible for many intriguing phenomena in diverse quantum-fluid systems. Having a theoretical model to reliably predict the vortex motion therefore promises a broad significance. But a grand challenge in developing such a model is to evaluate the dissipative force caused by thermal quasiparticles in the quantum fluids scattering off the vortex cores. Various models have been proposed, but it remains unclear which model describes reality due to the lack of comparative experimental data. Here we report a visualization study of quantized vortex rings propagating in superfluid helium. By examining how the vortex rings spontaneously decay, we provide decisive data to identify the model that best reproduces observations. This study helps to eliminate ambiguities about the dissipative force acting on vortices, which could have implications for research in various quantum-fluid systems that also involve similar forces, such as superfluid neutron stars and gravity-mapped holographic superfluids.

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Analysis of anisotropic subgrid-scale stress for coarse large-eddy simulation

Inagaki K., Kobayashi H.

Physical Review Fluids (Physical Review Fluids) 8 ( 10 ) 2023.10

This study discusses the necessity of anisotropic subgrid-scale (SGS) stress in large-eddy simulations (LESs) of turbulent shear flows using a coarse grid resolution. We decompose the SGS stress into two parts to observe the role of SGS stress in turbulent shear flows in addition to the energy transfer between grid-scale (GS or resolved scale) and SGS. One is the isotropic eddy-viscosity term, which contributes to energy transfer, and the other is the residual anisotropic term, which is separated from the energy transfer. We investigate the budget equation for GS Reynolds stress in turbulent channel flows accompanied by the SGS stress decomposition. In addition, we examine the medium and coarse filter length cases; the conventional eddy-viscosity models can fairly predict the mean velocity profile for the medium filter case and fails for the coarse filter case. The budget for GS turbulent kinetic energy shows that the anisotropic SGS stress has a negligible contribution to energy transfer. In contrast, the anisotropic stress has a large and nondissipative contribution to the streamwise and spanwise components of GS Reynolds stress when the filter size is large. Even for the medium-size filter case, the anisotropic stress contributes positively to the budget for the spanwise GS Reynolds stress. Spectral analysis of the budget reveals that the positive contribution is prominent at a scale consistent with the spacing of streaks in the near-wall region. Therefore, we infer that anisotropic stress contributes to the generation mechanism of coherent structures. Predicting the positive contribution of the anisotropic stress to the budget is key to further improving SGS models.

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Experimental and theoretical analyses on power generation characteristics of co-axial MHD energy conversion device

Hasebe T., Sasaki R., Fujino T., Takana H., Kobayashi H.

Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) (Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi)) 216 ( 3 ) 2023.09

ISSN 04247760

Experiments on power generation were conducted under the open-circuit condition to validate theoretical analyses on the power generation characteristics of a co-axial MHD energy conversion device. Considering distribution of externally applied magnetic field and the electromotive force induced by the rotation of the conductive inner cylinder, the results show that the experimental open-circuit voltage was lower than the theoretical one for the wide channel width, whereas the experimental open-circuit voltage was higher than the theoretical one for the narrow channel width. The inclination of the inner cylinder might cause the decrease in effective radial ratio.

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Evaporation behavior of liquid microdroplets in atmospheric-pressure nonequilibrium plasma

Nitta K., Muneoka H., Shimizu Y., Kobayashi H., Terashima K., Ito T.

Plasma Sources Science and Technology (Plasma Sources Science and Technology) 32 ( 5 ) 2023.05

ISSN 09630252

In recent years, atmospheric-pressure nonequilibrium plasma processing using microdroplets has attracted significant attention. To improve the controllability of this process, an understanding of the evaporation behavior of droplets in plasma is highly desirable. In this study, we examine the evaporation behavior of well-controlled inkjet droplets in atmospheric-pressure nonequilibrium argon plasma through both experiments and modeling. A comparison of the droplet evaporation model based on energy balance considering gas temperature, electron and ion collisions, and recombination reactions with experimental evaporation behavior suggests that droplet evaporation is enhanced in high-density plasma environments with electron and ion densities exceeding 1019 m−3 when compared with that in non-ionized gaseous environments at a gas temperature below 1000 K.

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Experimental and Theoretical Analyses on Power Generation Characteristics of Co-axial MHD Energy Conversion Device

Hasebe T., Sasaki R., Fujino T., Takana H., Kobayashi H.

IEEJ Transactions on Power and Energy (IEEJ Transactions on Power and Energy) 143 ( 7 ) 454 - 460 2023

ISSN 03854213

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Universal Anomalous Diffusion of Quantized Vortices in Ultraquantum Turbulence

Satoshi Yui, Yuan Tang, Wei Guo, Hiromichi Kobayashi, Makoto Tsubota

Physical Review Letters (American Physical Society) 129 ( 2 ) 025301 2022.07

Research paper (scientific journal), Accepted, ISSN 00319007

In classical viscous fluids, turbulent eddies are known to be responsible for the rapid spreading of embedded particles. However, in inviscid quantum fluids where the turbulence is induced by a chaotic tangle of quantized vortices, dispersion of the particles can be achieved via a nonclassical mechanism, i.e., their binding to the evolving vortices. However, knowledge on how the vortices diffuse and spread in quantum-fluid turbulence is very limited, especially for the so-called ultraquantum turbulence (UQT) generated by a random tangle of vortices. Here we report a systematic numerical study of the apparent diffusion of vortices in UQT in superfluid helium-4 using the full Biot-Savart simulation. We reveal that the vortices in the superfluid exhibit a universal anomalous diffusion (superdiffusion) at small times, which transits to normal diffusion at large times. This behavior is found to be the result of a generic scaling property of the vortex velocity. Our simulation at finite temperatures also nicely reproduces recent experimental observations. The knowledge obtained from this study may form the base for understanding turbulent transport and universal vortex dynamics in various quantum fluids.

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Transport and modeling of subgrid-scale turbulent kinetic energy in channel flows

Kazuhiro Inagaki, Hiromichi Kobayashi

AIP Advances (AIP Advances) 12 ( 4 ) 045222 2022.04

Research paper (scientific journal), Joint Work, Accepted

To develop a more convenient subgrid-scale (SGS) model that performs well even in coarse grid cases, we investigate the transport and modeling of SGS turbulent kinetic energy (hereafter SGS energy) in turbulent channel flows based on the stabilized mixed model (SMM). In this paper, we try to increase the convenience of the SMM by replacing the modeled transport equation for the SGS energy with an algebraic model. The SMM quantitatively adequately predicts the total turbulent kinetic energy of the direct numerical simulation (DNS) even in coarse grid cases. For both the filtered DNS (fDNS) and large-eddy simulation (LES), the statistically averaged production term balances with the dissipation in the region away from the wall in the SGS energy transport equation. In contrast, we reveal that the correlation coefficient between the production and dissipation terms is high for the modeled transport equation in LES, whereas that for the fDNS is low. Based on the high correlation or local equilibrium between the production and dissipation observed in the LES, we demonstrate the reduction of the SMM into a zero-equation SMM (ZE-SMM). We construct a new damping function based on the grid-scale Kolmogorov length to reproduce the near-wall behavior of the algebraic model for the SGS energy. The ZE-SMM provides quantitatively the same performance as the original SMM that employs the SGS energy transport model. This result suggests that the local equilibrium model for the SGS energy provides the equivalent performance as the transport model in wall-bounded turbulent flows even in coarse grid cases.

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Quasi-Two-Dimensional Numerical Analysis of Influence of Taylor Vortex and Eddy Current on Generation Characteristics of Co-axial MHD Energy Conversion Device under Laminar Flow

Sasaki R., Fujino T., Takana H., Kobayashi H.

IEEJ Transactions on Power and Energy (IEEJ Transactions on Power and Energy) 142 ( 5 ) 268 - 274 2022

ISSN 03854213

Quasi-two-dimensional magnetohydrodynamic (MHD) numerical simulation was conducted to clarify the power generation characteristics of a co-axial MHD energy conversion device under laminar flow. The numerical results were compared with one-dimensional theoretical results in the radial direction. For a fixed load resistance, the dependence of output power and efficiency on Hartmann number, which is proportional to the magnetic flux density, was investigated. We found the decrease in mean velocity and the increase in viscous wall shear stress owing to upper and lower walls, the increase in viscous wall shear stress owing to Taylor vortex cells, and the increase in Joule heating owing to eddy current in the MHD numerical simulation compared to those in the one-dimensional theoretical analysis.

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LES OF MHD TURBULENT TAYLOR-COUETTE FLOW IN AXIAL MAGNETIC FIELD

Kobayashi H., Sasaki R., Fujino T., Takana H.

12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022 (12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022) 2022

Large eddy simulation (LES) of magnetohydrodynamic (MHD) turbulent Taylor-Couette (TC) flows is conducted to reveal the effect of the Hartmann number proportional to the axial magnetic field strength on the flow and electric current fields. The upper-lower walls are insulated and the inner-outer sidewalls are set to insulating walls (open condition) or perfectly conducting walls (short condition). As increasing the Hartmann number, turbulent fluctuations are suppressed, and the turbulent flow distributions approach the MHD laminar flow distributions. The orientations of turbulent vortices change from the azimuthal flow direction to the axial magnetic field direction even in the TC flow. The triplet high-speed streaky structures are uncovered near the inner wall.

INVESTIGATION OF SUBGRID-SCALE TURBULENT KINETIC ENERGY IN CHANNEL FLOWS

Inagaki K., Kobayashi H.

12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022 (12th International Symposium on Turbulence and Shear Flow Phenomena, TSFP 2022) 2022

We investigate the subgrid-scale (SGS) turbulent kinetic energy (hereafter referred to as SGS energy) and its transport equation by employing the stabilized mixed model (SMM) developed by Abe (2013). The prediction of the budget for the modeled transport equation is qualitatively well compared with the filtered DNS via the Gaussian filter. In addition, the production term balances with the dissipation rate in the outer region, which suggests that the transport equation can be reduced by assuming the equilibrium between them. We investigate five algebraic expressions for the SGS energy. Among them, the equilibrium form with a newly introduced damping function yields the best compared with the SMM. The zero-equation SMM (ZE-SMM) that employs the equilibrium form instead of the transport equation for the SGS energy provides quantitatively equivalent results as the original SMM. This study paves the way for constructing a convenient anisotropic SGS model that is robust even in coarse grid resolutions.

Tree Cutting Approach for Domain Partitioning on Forest-of-Octrees-based Block-structured Static Adaptive Mesh Refinement with Lattice Boltzmann Method

Yuta Hasegawa, Takayuki Aoki, Hiromichi Kobayashi, Yasuhiro Idomura, Naoyuki Onodera

Parallel Computing (Parallel Computing) 108 102851 2021.12

Research paper (scientific journal), Accepted, ISSN 01678191

The aerodynamics simulation code based on the lattice Boltzmann method (LBM) using forest-of-octrees-based block-structured adaptive mesh refinement (AMR) with temporary-fixed refinement was implemented, and its performance was evaluated on GPU-based supercomputers. Although the Space-Filling-Curve-based (SFC) domain partitioning algorithm for the octree-based AMR has been widely used on conventional CPU-based supercomputers, accelerated computation on GPU-based supercomputers revealed a bottleneck due to costly halo data communication. Our new tree cutting approach adopts a hybrid domain partitioning with the coarse structured block decomposition and the SFC partitioning in each block. This hybrid approach improved the locality and the topology of the partitioned sub-domains and reduced the amount of the halo communication to one-third of the original SFC approach. In the strong scaling test, the code achieved maximum ×1.82 speedup at the performance of 2207 MLUPS (mega-lattice update per second) on 128 GPUs (NVIDIA® Tesla® V100). In the weak scaling test, the code achieved 9620 MLUPS at 128 GPUs with 4.473 billion grid points, while keeping the parallel efficiency of 93.4% from 8 to 128 GPUs.

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Theoretical Analysis on Power Generation Characteristics for Co-axial MHD Energy Conversion Device

Sasaki R., Fujino T., Takana H., Kobayashi H.

IEEJ Transactions on Power and Energy (IEEJ) 141 ( 10 ) 642 - 648 2021.10

Research paper (scientific journal), Joint Work, Accepted, ISSN 03854213

Theoretical solution is derived for power generation efficiency and electrical output power of the co-axial MHD energy conversion device using liquid metal. Although the electrical output power is proportional to the square of Reynolds number, the power generation efficiency is independent of Reynolds number. The energy input to the liquid metal is converted into electrical output power, viscous and Joule dissipation. For obtaining high power generation efficiency, viscous and Joule dissipation should be minimized. The combination of Hartmann number and electrical resistance ratio exists for the maximum power generation efficiency under the condition of the weak MHD interaction rather than that of the maximum electrical output power. The theoretical analysis clearly shows that the maximum power generation efficiency of the co-axial MHD energy conversion device is 1/3 ≈ 33.3% at the highest.

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Aerodynamic Study on Rotating Baseball with Low Spin Rates (Drop Mechanism of “Forkball” or “Splitter”)

Ryoga Ohashi, Takayuki Aoki, Seiya Watanabe, Hiromichi Kobayashi

日本流体力学会誌ながれ (日本流体力学会) 40 ( 5 ) 343 - 355 2021.10

Research paper (scientific journal), Joint Work, Accepted

Theoretical analysis of annular laminar flows with MHD interaction driven by rotating co-axial cylinder

Sasaki R., Fujino T., Takana H., Kobayashi H.

Electronics and Communications in Japan (Willy) 104 ( 2 ) 2021.06

Research paper (scientific journal), Joint Work, Accepted, ISSN 19429533

Theoretical solution is derived for annular laminar flows with MHD interaction driven by a rotating co-axial cylinder. The effects on the flow field and rotational torque are clarified by changing the radius ratio and the strength of MHD interaction. As the radius ratio increases, azimuthal flow velocity increases and approaches the plane Couette flow profile for weak MHD interaction. The azimuthal flow velocity, however, decreases as the MHD interaction increases, and the reverse flow emerges in large radial locations. As the MHD interaction increases, the rotational torque increases. A larger radius ratio leads to the larger sensitivity of the change in rotational torque.

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Quantum Turbulence Coupled with Externally Driven Normal-Fluid Turbulence in Superfluid 4He

Satoshi Yui, Hiromichi Kobayashi, Makoto Tsubota, Rio Yokota

arXiv 2021.03

Research paper (scientific journal), Joint Work

Theoretical analysis of annular laminar flows with MHD interaction driven by rotating co-axial cylinder

Sasaki R., Fujino T., Takana H., Kobayashi H.

IEEJ Transactions on Power and Energy (IEEJ) 141 ( 3 ) 280 - 286 2021.03

Research paper (scientific journal), Joint Work, Accepted, ISSN 03854213

Theoretical solution is derived for annular laminar flows with MHD interaction driven by a rotating co-axial cylinder. The effects on the flow field and rotational torque are clarified by changing the radius ratio and the strength of MHD interaction. As increasing the radius ratio, azimuthal flow velocity increases and approaches the plane Couette flow profile for weak MHD interaction. The azimuthal flow velocity, however, decreases as increasing MHD interaction, and the reverse flow emerges in large radial locations. As increasing the MHD interaction, the rotational torque increases. A larger radius ratio leads to the larger sensitivity of the change in rotational torque.

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Role of various scale-similarity models in stabilized mixed subgrid-scale model

Inagaki K., Kobayashi H.

Physics of Fluids (Physics of Fluids) 32 ( 7 ) 2020.07

ISSN 10706631

© 2020 Author(s). We investigate the physical role of various scale-similarity models in the stabilized mixed model [K. Abe, "An improved anisotropy-resolving subgrid-scale model with the aid of a scale-similarity modeling concept,"Int. J. Heat Fluid Flow 39, 42 (2013); M. Inagaki and K. Abe, "An improved anisotropy-resolving subgrid-scale model for flows in laminar-turbulent transition region,"Int. J. Heat Fluid Flow 64, 137 (2017)] and evaluate their performance in turbulent channel flows. Among various models in the present study, the original model combined with the scale-similarity model for the subgrid-scale (SGS)-Reynolds term yields the best prediction for the anisotropy of the grid-scale (GS) velocity fluctuations and the SGS stress, even in coarse grid resolutions. Moreover, it successfully predicts large intensities of the spectra close to the cut-off scale in accordance with the filtered direct numerical simulation, whereas other models predict a rapid decay of the spectra in the low-wavelength region. To investigate the behavior of the models close to the cut-off scale, we analyze the budget equation for the GS Reynolds stress spectrum. The result shows that the scale-similarity model for the SGS-Reynolds term plays a role in the enhancement of the wall-normal velocity fluctuation close to the cut-off scale. Thereby, it activates turbulence close to the cut-off scale, leading to a reproduction of the proper streak structures observed in wall-bounded turbulent flows. The reproduction of velocity fluctuations close to the cut-off scale and turbulent structures is a key element for further development of SGS models.

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Fully Coupled Two-Fluid Dynamics in Superfluid He 4: Anomalous Anisotropic Velocity Fluctuations in Counterflow

Satoshi Yui, Hiromichi Kobayashi, Makoto Tsubota, Wei Guo

Physical Review Letters (American Physical Society) 124 ( 15 ) 2020.04

Research paper (scientific journal), Accepted, ISSN 00319007

© 2020 American Physical Society. We investigate the thermal counterflow of the superfluid He4 by numerically simulating three-dimensional fully coupled dynamics of the two fluids, namely quantized vortices and a normal fluid. We analyze the velocity fluctuations of the laminar normal fluid arising from the mutual friction with the quantum turbulence of the superfluid component. The streamwise fluctuations exhibit higher intensity and longer-range autocorrelation, as compared to transverse ones. The anomalous fluctuations are consistent with visualization experiments [Mastracci et al., Phys. Rev. Fluids 4, 083305 (2019)PLFHBR2469-990X10.1103/PhysRevFluids.4.083305], and our results confirm their analysis with simple models on the anisotropic fluctuations. This success validates the model of the fully coupled dynamics and paves the way for solving some outstanding problems in this two-fluid system.

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Regularized, parameter free scale similarity type models for Large Eddy Simulation

Klein M., Ketterl S., Engelmann L., Kempf A., Kobayashi H.

International Journal of Heat and Fluid Flow (International Journal of Heat and Fluid Flow) 81 2020.02

ISSN 0142727X

© 2019 Elsevier Inc. The fidelity of Large Eddy Simulations (LES) depends strongly on the closures of the sub-grid scale (SGS) stress tensor. Although it is well known that the SGS stresses in LES are not aligned with the strain rate tensor, the most widely used models are still of eddy viscosity type, due to their robust behavior in LES and reasonable performance in a posteriori testing. The unstable behavior of more advanced anisotropic models, that is typically found in LES, has been attributed to either the fact that these models provide backscatter or to the fact that they do not provide a sufficient amount of dissipation. Based on recent advances in the field, an alternative modeling strategy is suggested, which can be used to regularize an arbitrary anisotropic (e.g. scale similarity type) model. The resulting model is easy to implement, can be written in compact form and is free of model parameters. The model has been tested a-posteriori and results are presented for a Taylor-Green-Vortex, a free plane jet and a turbulent channel flow of friction Reynolds numbers 395, 590 and 934. The results are compared to well-known eddy viscosity models and when applicable, to simulations without explicit LES model. The new model exhibits good performance for a variety of mesh resolutions and for all configurations. Furthermore, a-priori analysis results in the context of liquid atomization indicate that the model might be suitable as well in more complex physical scenarios. The a-priori analysis performance of the model is found to be nearly equivalent to the underlying structural anisotropic model in terms of its correlation coefficient, but the model is free of backscatter and provides good stability in LES.

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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

© 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

© 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

© 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

スタンフォード大学の紹介

小林宏充

日本流体力学会誌ながれ (日本流体力学会) 26 ( 5 ) 345-348 2007.10

Research paper (other academic), Single Work

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

Hiromichi Kobayashi

Center for Turbulence Research Annual Research Briefs 2006 (Center for Turbulence Research) 69-77 2006.12

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

Backward-facing step calculations using the Shear Improved Smagorinsky Model

Federico Toschi, Hiromichi Kobayashi, Ugo Piomelli, Gianluca Iaccarino

Center for Turbulence Research Proceedings of the 2006 Summer Program (Center for Turbulence Research) 87-97 2006.12

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

Can a spinning egg really jump?

Takahisa Mitsui, Kesao Aihara, Chikako Terayama, Hiromichi Kobayashi, and Yutaka Shimomura

Proceedings of the Royal Society A 462 ( 2074 ) 2897-2905 2006.10

Research paper (scientific journal), Joint Work, Accepted

Large eddy simulation of magnetohydrodynamic turbulent channel flows with local subgrid-scale model based on coherent structures

Hiromichi Kobayashi

Physics of Fluids (American Institute of Physics) 18 ( 4 ) 045107 2006.04

Research paper (scientific journal), Single Work, Accepted

A new methodology for Reynolds-averaged modeling based on the amalgamation of heuristic-modeling and turbulence-theory methods

Akira Yoshizawa, Shoiti Nisizima, Yutaka Shimomura, Hiromichi Kobayashi, Yuichi Matsuo, Hiroyuki Abe, and Hitoshi Fujiwara

Physics of Fluids (American Institute of Physics) 18 ( 3 ) 035109 2006.03

Research paper (scientific journal), Joint Work, Accepted

LES of MHD turbulent channel flows with a local SGS model based on coherent structures

Hiromichi Kobayashi

Center for Turbulence Research Annual Research Briefs 2005 (Center for Turbulence Research) 235-247 2005.12

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

The subgrid-scale models based on coherent structures for rotating homogeneous turbulence and turbulent channel flow

Hiromichi Kobayashi

Physics of Fluids (American Institute of Physics) 17 ( 4 ) 045104 2005.04

Research paper (scientific journal), Single Work, Accepted

The subgrid-scale (SGS) models based on the coherent structure (CS) in grid-scale flow fields are proposed and are applied to (non-)rotating homogeneous turbulences and turbulent channel flows. The eddy viscosity is modeled by a coherent structure function (CSF) with a fixed model-parameter. The CSF is defined as the second invariant normalized by the magnitude of a velocity gradient tensor and plays a role of wall damping. The probability density function of the CSF is non-Gaussian showing an intermittency effect. The model parameter is locally determined, and it is always positive and has a small variance. These models satisfy a correct asymptotic behavior to a wall for incompressible flows. It is shown that the SGS models with an energy-decay suppression function which indicates also a pseudo-backscatter are consistent with the asymptotic material frame indifference in a rotating frame. Since the CSF characterizing turbulent flows has relation to the SGS energy dissipation, the present SGS models are applicable not only to (non-)rotating homogeneous and shear turbulences but also to laminar flows. The proposed models have almost the same performance as the dynamic Smagorinsky model for (non-)rotating homogeneous turbulences and turbulent channel flows, but these models do not need to average or clip the model parameter, use an explicit wall-damping function, or change the fixed-parameter, so that they are suitable for engineering applications of LES.

R-z Two-dimensional Numerical Simulations of a Frozen Inert Gas Plasma MHD Generator

Hiromichi Kobayashi, Seiji Nagai, Yoshihiro Okuno

IEEE Transactions on Plasma Science (The Institute of Electrical and Electronics Engineers) 33 ( 1 ) 197-204 2005.02

Research paper (scientific journal), Joint Work, Accepted

In a magnetohydrodynamics (MHD) power generation with a frozen inert gas plasma (FIP), the effect of the non-uniformity of the inlet plasma in the direction perpendicular to walls on the performance and the comparison of the performance with r-theta two-dimensional (2-D) numerical simulations are examined with r-z 2-D ones. The inlet non-uniformity of an ionization degree is kept throughout the channel and even in the boundary layer the state of the FIP is realized without an ionization instability. When the inlet ionization degree near the walls is higher than that in the main flow, the enthalpy extraction ratio decreases because the strong MHD interaction near the wall leads to the development of the boundary layer. On the other hand, it increases for the inverse distribution at the channel inlet, even if the introduced total inlet ionization degree is the same. In comparison with the results obtained
from the r-theta simulation, the development of the boundary layer results in the deterioration of the performance, and the optimal condition shifts to the low inlet ionization degree and the high load resistance.

Large Eddy Simulation for the Dynamic Clark Model with an Anisotropic Filter

Hiromichi Kobayashi

Hiyoshi Review of Natural Science, Keio University (慶応義塾大学出版会) ( 36 ) 15-25 2004.09

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

大学一年生の物理への関心度と知識度調査

加藤万里子，小林宏充，鹿野川正彦

慶應義塾大学日吉紀要 (慶應義塾大学出版会) ( 35 ) 45-61 2004.03

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

Response to "Comment on 'Inapplicability of the dynamic Clark model to the large eddy simulation of incompressible tubulent channel flows'"

Hiromichi Kobayashi, Yutaka Shimomura

Physics of Fluids (American Institute of Physics) 16 ( 2 ) 492 2004.02

Research paper (scientific journal), Joint Work, Accepted

高温空気燃焼ボイラの熱特性に関する研究（第２報，数値計算による検討）

小林宏充，吉川邦夫

日本機械学会論文集Ｂ (日本機械学会) 69 ( 686 ) 2330-2336 2003.10

Research paper (scientific journal), Joint Work, Accepted

Thermal characteristics of a high temperature air combustion boiler is numerically examined. The high temperature air combustion is realized using a preheated air of about 800℃〜1000℃ under low oxygen content (〜5%). Numerical simulation reveals that more uniform temperature distribution in the boiler and higher heat transfer are obtainable using high temperature air in comparison with using normal temperature air owing to mild reactions in the high temperature field and heat recovery by regenerative burners. High speed injection of high temperature air into the boiler causes in-furnace exhaust gas recirculation, which results in low NOx emission. There is good agreement between experiment and numerical simulation in particular when using low calorific value gas, because more uniform temperature distribution is realized and average temperature in the boiler becomes lower.

Inapplicability of the dynamic Clark model to the large eddy simulation of incompressible turbulent channel flows

Hiromichi Kobayashi, Yutaka Shimomura

Physics of Fluids (American Institute of Physics) 15 ( 3 ) L29-L32 2003.03

Research paper (scientific journal), Joint Work, Accepted

Numerical Study on Performance of Disk MHD Generator Using Frozen Inert Gas Plasma

Hiromichi Kobayashi, Yukimasa Satou, Yoshihiro Okuno

IEEE Transactions on Plasma Science (The Institute of Electrical and Electronics Engineers) 30 ( 6 ) 2152-2159 2002.12

Research paper (scientific journal), Joint Work, Accepted

In an MHD generator using a frozen inert gas plasma (FIP), the availability of a frozen argon plasma, the influence of plasma uniformity at the generator inlet on the performance, and the feasibility of a large-scale generator are numerically examined by r-theta two-dimensional imulation. The FIP is produced by pre-ionizing inert gas without an alkali metal seed at the generator inlet, then the ionization degree of the plasma is kept almost constant in the whole of the channel because of considerable slow recombination of the inert gas just like frozen reaction plasma. It is found that not only helium but also argon frozen plasma MHD generation is realized, although highly accurate control of inlet onization degree is necessary for argon. It is important to reduce the nonuniformity of plasma properties at the generator inlet in order to raise the maximum enthalpy extraction ratio. Even for the large-scale generator with 1000MW thermal input, the ionization degree is kept almost constant in the whole of the channel and the high performance is obtainable. This result is extremely attractive for the FIP MHD generator.

Performance of High Temperature Air Combustion Boiler with Low NOx Emission

Hiromichi Kobayashi, Yohito Ito, Naoki Tsuruta, Kunio Yoshikawa

JSME International Journal, Series B (Japanese Society of Mechanical Engineering) 45 ( 3 ) 481-486 2002.08

Research paper (scientific journal), Joint Work, Accepted

Thermal performance in the experiments and three-dimensional numerical simulations for a high temperature air combustion boiler where fuel can be efficiently combusted by high temperature preheated air (800C-1000C) is examined. The boiler can burn not only natural gas but also low calorific gas (e.g. full gasification gas obtained from coal or wastes). In the boiler, four regenerative burners are installed. This boiler has new features that not only air but also gasification gas is heated up to 900C, and combination of burners is switched every 15 seconds where two burners are used as inlets of fuel and air and the other two burners are used as outlets of exhaust gas. Natural gas and syngas obtained from coal are burned. The NOx emission for each fuel is less than 50ppm. The heat transfer of three-dimensional calculation is predicted higher than that of experiment.

High Temperature Air Combustion Boiler for Low BTU Gas

K.Kawai, K.Yoshikawa, H.Kobayashi, J.S.Tsai, M.Matsuo and H.Katsushima

Energy Conversion and Management (Elsevier Science) 43 ( 9-12 ) 1563-1570 2002.06

Research paper (scientific journal), Joint Work, Accepted

A new concept boiler where fuel can be efficiently combusted by high temperature preheated air is proposed and experimental demonstration is done. This boiler is suitable for low BTU gas derived from gasification process of coal and wastes with no dioxin emission. This boiler is characterized by the following features; uniform heat flux field, augmentation of heat transfer, reduction of combustion noise level, suppression of NOx emission and compactness. Preliminary experiments using natural gas as a fuel demonstrate above distinct performance as well as good agreement with three-dimensional numerical simulation.

高温空気燃焼ボイラの熱特性に関する研究（第１報，実験による検討）

小林宏充，吉川邦夫

日本機械学会論文集Ｂ (日本機械学会) 67 ( 633 ) 2877-2882 2001.11

Research paper (scientific journal), Joint Work, Accepted

A new concept compact boiler using high temperature air is proposed and experimental demonstration is done. In the boiler, high temperature air combustion is realized. Fuel can be efficiently burned by high temperature preheated air of about 800C-1000C under low oxygen content ( < 5% ). The temperature distribution in the furnace is very uniform and there is no hot spot, so that low NOx emission ( < 40ppm) and relatively high average temperature in the furnace can be achieved. Thermal efficiency of more than 90% is accomplished including waste heat recovery of exhaust gas. This boiler is useful to partial load operation, because the response of thermal output is linear. This boiler is also suitable for low calorific value gas derived from gasification process of coal and wastes with no dioxin emission. Simulated low calorific value gas made from natural gas diluted with argon can be burned with low NOx emission.

凍結希ガスプラズマを利用したディスク形MHD発電機の性能数値計算

小林宏充，佐藤幸正，奥野喜裕

電気学会論文誌Ｂ (電気学会) 121 ( 8 ) 1023-1028 2001.08

Research paper (scientific journal), Joint Work, Accepted

MHD electrical power generation with frozen helium plasma (FHP) is examined numerically. The FHP can be initiated by pre-ionized helium without the alkali metal seed at the generator inlet. Since the three-body recombination coefficient of helium ions is low at the electron temperature above 5000K, the ionization degree can be kept almost constant in the entire region of the generator channel. The r-theta two-dimensional numerical results show that the performance of the FHP MHD generator is comparable to that of the seeded plasma MHD generator, if the additional power consumed to pre-ionization is ignored. In the FHP MHD generator, the ionization degree at the inlet should be controlled precisely, as well as the seed fraction in the seeded plasma MHD generator. Under the adequate inlet ionization degree for sustaining the FHP plasma, the plasma maintains the uniform structure. On the other hand, a slightly excess ionization degree causes the strong Lorentz force in the upstream region of the generator, then the generator performance is deteriorated.

The Performance of Dynamic Subgrid-Scale Models in the Large Eddy Simulation of Rotating Homogeneous Turbulence

Hiromichi Kobayashi, Yutaka Shimomura

Physics of Fluids (American Institute of Physics) 13 ( 8 ) 2350-2360 2001.08

Research paper (scientific journal), Joint Work, Accepted

The performance of dynamic subgrid-scale models is numerically examined in the large eddy simulation (LES) of rotating homogeneous turbulences in comparison with the corresponding filtered data of the direct numerical simulation (DNS). The examined dynamic SGS models are: the dynamic Smagorinsky model (DSM), the dynamic mixed model (DMM), the dynamic Clark model (DCM), and the dynamic two-parameter Clark model (DTCM). All models are mathematically reformulated in a rotating frame from the corresponding expressions in an inertial frame. It is shown that the DSM and the DMM are not consistent with the constraint of asymptotic material frame indifference, but the DCM and the DTCM are consistent. All models except the DSM show similar decays of the grid-scale turbulent energies both in non-rotating and in rotating frames; they agree well with the DNS in the non-rotating case, but they are slightly less dissipative than the DNS in the rotating case. The DSM underestimated the GS energy dissipation in the non-rotating case, though there is no major difference from other models in the rotating case. However, the DSM in a rotating frame, which takes a different form from that in an inertial frame, leads to an unphysical fluctuating decay for a homogeneous turbulence suddenly submitted to a rotation.

MHD(電磁流体力学)発電機内におけるプラズマ流の3次元数値シミュレーション

小林宏充

慶應義塾大学日吉紀要 (慶応義塾大学出版会) ( 28 ) 39-46 2000.09

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

Feasibility Study on Frozen Inert Gas Plasma MHD Generator

Hiromichi Kobayashi, Yoshihiro Okuno

IEEE Transactions on Plasma Science (The Institute of Electrical and Electronics Engineers) 28 ( 4 ) 1296-1302 2000.08

Research paper (scientific journal), Joint Work, Accepted

The feasibility of an MHD generator with frozen inert gas plasma is examined numerically. The frozen inert gas plasma is produced by pre-ionizing helium of inert gas without alkali metal seed at the generator inlet. Since the three-body recombination coefficient of helium ions is low at
the electron temperature more than 5000K, the ionization degree of inert gas is kept almost constant in the entire region of the generator channel and the relation between the electron temperature and the electron number density deviates from the Saha equilibrium. In a small scale disk shaped generator, the enthalpy extraction ratio of 22.7% and the isentropic efficiency of 54.8% are obtainable for the load resistance of 3.0Omega and magnetic flux density of 4T under the pre-ionization degree of 4.79x10^{-5}. The auxiliary power to sustain the pre-ionized plasma corresponds to about 2% of the thermal input. For high magnetic flux density, the generator performance can be improved as well as a conventional seeded plasma MHD generator.

CIP法によるMHD発電機内プラズマ・流体の３次元シミュレーション

小林宏充，奥野喜裕，椛島成治

数値流体力学会誌 (数値流体力学会) 8 ( 3 ) 130-136 2000.04

Research paper (scientific journal), Joint Work

高温空気を用いた石炭・廃棄物ガス化発電システム

小林宏充，吉川邦夫，塩田進

日本機械学会論文集Ｂ (日本機械学会) 66 ( 641 ) 235-240 2000.01

Research paper (scientific journal), Joint Work, Accepted

A new concept of gasification power generation systems fueled by coal, RDF and various kinds of wastes using high temperature air is proposed. Cycle analyses of these IGCC and boiler systems are done. The calculation shows that heating value of syngas almost doubles when we increase the gasification air temperature from 25C to 1000C. More than 45% thermal efficiency is obtainable both for coal and RDF by employing the new high temperature air blown IGCC system. This IGCC system is applicable to various wastes including low grade wastes such as sludge.

亜音速非平衡ディスク形MHD発電機内の流れと発電性能

名原啓博，小林宏充，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 119 ( 8/9 ) 931-936 1999.08

Research paper (scientific journal), Joint Work, Accepted

入口スワールをもつ非平衡ディスク形MHD発電機内プラズマ・流体の三次元構造

清水和弥，小林宏充，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 119 ( 7 ) 828-833 1999.07

Research paper (scientific journal), Joint Work, Accepted

Three-Dimensional Simulation of Plasma and Flow in a Disk MHD Generator by Using CIP Method

Hiromichi Kobayashi, Yoshihiro Okuno, Shigeharu Kabashima

Computational Fluid Dynamics JOURNAL (Intern'l Society of CFD) 8 ( 1 ) 50-55 1999.04

Research paper (scientific journal), Joint Work, Accepted

非平衡ディスク形MHD発電機における放電構造と発電性能に及ぼす背圧の影響

藤野貴康，小林宏充，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 119 ( 1 ) 97-102 1999.01

Research paper (scientific journal), Joint Work, Accepted

熱入力100MW非平衡ディスク形MHD発電機におけるプラズマ・流体の三次元構造

清水和弥，小林宏充，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 119 ( 1 ) 103-108 1999.01

Research paper (scientific journal), Joint Work, Accepted

Three-Dimensional Structures of MHD Flow in a Disk Generator

Hiromichi Kobayashi, Yoshihiro Okuno, Shigeharu Kabashima

IEEE Transactions on Plasma Science (The Institute of Electrical and Electronics Engineers) 26 ( 5 ) 1526-1531 1998.10

Research paper (scientific journal), Joint Work, Accepted

亜音速ディスク形CCMHD発電機の部分負荷運転特性

名原啓博，小林宏充，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 118 ( 9 ) 1041-1046 1998.09

Research paper (scientific journal), Joint Work, Accepted

非平衡MHD発電におけるプラズマ擾乱の三次元挙動

村上貴裕，小林宏充，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 118 ( 5 ) 587-592 1998.05

Research paper (scientific journal), Joint Work, Accepted

亜音速ディスク形CCMHD発電機の電圧－電流特性

小林宏充，桑子奈津子，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 118 ( 3 ) 302-307 1998.03

Research paper (scientific journal), Joint Work, Accepted

空間的なシード不均一下での非平衡ディスク形MHD発電機内プラズマの挙動

村上貴裕，小林宏充，奥野喜裕，椛島成治

電気学会論文誌Ｂ (電気学会) 117 ( 5 ) 665-670 1997.05

Research paper (scientific journal), Joint Work, Accepted

Three-Dimensional Simulation of Nonequilibrium Seeded Plasma in Closed Cycle Disk MHD Generator

Hiromichi Kobayashi, Yoshihiro Okuno, Shigeharu Kabashima

IEEE Transactions on Plasma Science (The Institute of Electrical and Electronics Engineers) 25 ( 2 ) 380-385 1997.02

Research paper (scientific journal), Joint Work, Accepted

ディスク形ＣＣＭＨＤ発電機の性能に与える入口圧力変動の影響

Kobayashi Hiromicih, Okuno Yoshihiro, Kabashima Shigeharu

電気学会論文誌Ｂ (電気学会) 116 ( 6 ) 718-723 1996.06

Research paper (scientific journal), Joint Work, Accepted

非平衡ディスク形ＭＨＤ発電機における分割負荷による性能改善

Kobayashi Hiromichi, Okuno Yoshihiro, Kabashima Shigeharu

電気学会論文誌Ｂ (電気学会) 115 ( 9 ) 1104-1109 1995.09

Research paper (scientific journal), Joint Work, Accepted

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