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271 results on '"Yamamoto, Kyoji"'

104. Scattering Properties of Gas Molecules on a Water Adsorbed Surface.

Author

Takeuchi, Hideki, Yamamoto, Kyoji, and Hyakutake, Toru

Subjects
*RAREFIED gas dynamics, *SCATTERING (Physics), *MOLECULAR dynamics, *MOLECULE-molecule collisions, *METALLIC surfaces, *PLATINUM, *MONTE Carlo method, *GAS absorption & adsorption, *WATER, *DISTRIBUTION (Probability theory)
Abstract

The thermal problem of a rarefied argon (Ar) gas between two parallel walls is considered to investigate the characteristics of the reflected gas molecule at a platinum (Pt) wall surface which physically adsorbs water (H2O) molecules. The analysis is based on the molecular dynamics (MD) method for the interaction of gas molecules with the water adsorbed wall surface together with the direct simulation Monte-Carlo (DSMC) method for the motion of gas molecule. The accommodation coefficients of energy and normal momentum are obtained. The temperature distribution between two walls and the velocity distribution function of the reflected molecule are also obtained. It is found that the accommodation coefficients for the water adsorbed surface decrease with increasing the adsorption rate. [ABSTRACT FROM AUTHOR]

Published
2011
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114. Flow of Gas Mixtures through Micro Channel.

Author

Hyakutake, Toru, Yamamoto, Kyoji, and Takeuchi, Hideki

Subjects
*GAS flow, *GAS dynamics, *RAREFIED gas dynamics, *SPACE fluid dynamics, *MOLECULAR dynamics, *DYNAMICS
Abstract

To investigate flow of gas mixtures through micro channel in detail, the tangential momentum accommodation coefficients of each species for gaseous mixtures were determined by analyzing the Couette flow problem of a slightly rarefied gas between two walls. The molecular dynamics (MD) method for the interaction of gas molecule with the wall surface is combined with the DSMC method for the motion of gas molecules. These obtained accommodation coefficients were applied for the flow of gas mixture through the micro channel as the Maxwell-type boundary conditions, and influence of the surface with adsorbates and the gas concentration on the flow rate of the micro channel was examined. The simulation results show that the velocity slip and the accommodation coefficients for gas mixtures differ from that for a single gas. The differences of the molar concentration of gas mixtures and wall characteristics lead to variations of the flow rate in the channel. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2005
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115. Behavior of the Reflected Molecules of a Diatomic Gas at a Solid Surface.

Author

Takeuchi, Hideki, Yamamoto, Kyoji, and Hyakutake, Toru

Subjects
*DIATOMIC molecules, *SURFACE chemistry, *MOLECULAR dynamics, *COAL gas, *PHYSICAL & theoretical chemistry, *SURFACES (Physics)
Abstract

The N2 gas — Pt wall interaction is investigated for the Couette flow. The wall temperature is taken to be 300K. The method of analysis is based on the molecular dynamics method for interaction of gas molecules with a solid wall together with the DSMC method for the motion of gas molecules. Two cases of wall surface are considered: smooth surface and the surface with adsorbates. The momentum and energy accommodation coefficients are obtained. The velocity and energy distribution functions of the reflected molecules are also obtained. It is found that the Maxwell-type distribution function for the translational and rotational energy describes well the distribution function of the reflected molecules. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2005
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116. Numerical Simulation of Rarefied Plume Flow Exhausting from a Small Nozzle.

Author

Hyakutake, Toru and Yamamoto, Kyoji

Subjects
*NOZZLES, *MONTE Carlo method, *RAREFIED gas dynamics
Abstract

This paper describes the numerical studies of a rarefied plume flow expanding through a nozzle into a vacuum, especially focusing on investigating the nozzle performance, the angular distributions of molecular flux in the nozzle plume and the influence of the backflow contamination for the variation of nozzle geometries and gas/surface interaction models. The direct simulation Monte Carlo (DSMC) method is employed for determining inside the nozzle and in the nozzle plume. The simulation results indicate that the half-angle of the diverging section in the highest thrust coeficient is 25[SUP°]-30[SUP°] and this value varies with the expansion ratio of the nozzle. The descent of the half-angle brings about the increase of the molecules that are scattered in the backflow region. [ABSTRACT FROM AUTHOR]

Published
2003

147. Fibromatosis of the mesoappendix.

Author

Kimura, Noriko, Pilichowska, Monika, Yamazaki, Hideo, Ohuchi, Akio, and Yamamoto, Kyoji

Subjects
MESENCHYME tumors, APPENDIX diseases, IMMUNOHISTOCHEMISTRY, DIAGNOSIS
Abstract

Mesenchymal tumors of the appendix are very rare. Mesenteric fibromatosis is the most common diagnosis in the case of isolated proliferative fibroblastic lesion found in this region. However, the differential diagnosis between fibromatosis and well-differentiated fibrosarcoma (Grade I) can be difficult in some borderline cases. A rare case of proliferative fibroblastic lesion involving the appendix and mesoappendix is presented, and its origin, diagnosis and differential diagnosis are discussed. [ABSTRACT FROM AUTHOR]

Published
2000

148. Thermophoresis of a spherical particle in a rarefied gas of a transition regime.

Author

Yamamoto, Kyoji and Ishihara, Yuji

Subjects
*RAREFIED gas dynamics, *TEMPERATURE, *DENSITY
Abstract

A theoretical study is made of thermophoresis of a solid sphere in a rarefied gas in which a uniform temperature gradient and a uniform velocity at infinity exist. The analysis is carried out on the basis of the linearized Bhatnager-Gross-Krook (BGK) equation, from which simultaneous integral equations for the density, flow velocity, and temperature are derived. These equations are solved numerically over a wide range of Knudsen numbers covering the area from the slip flow to the nearly free molecular flow. A formula for the variation of the thermophoretic force acting on the sphere versus the Knudsen number is obtained for any value of thermal conductivity of the sphere when there is no imposed flow at infinity. The thermophoretic velocity of a suspended sphere in a gas is also calculated. The flow patterns as well as the distributions of temperature are shown. [ABSTRACT FROM AUTHOR]

Published
1988
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149. Flow of a rarefied gas past a circular cylinder.

Author

Yamamoto, Kyoji and Sera, Kazuyuki

Subjects
*CYLINDER (Shapes), *MACH number, *PHYSICS
Abstract

The flow of a rarefied gas past a circular cylinder at low Mach numbers is studied on the basis of the linearized Bhatnager–Gross–Krook model equation. The flow field is divided into two regions: the kinetic region adjacent to the cylinder and the near continuum region outside it. The Oseen–Stokes equation is treated in the near continuum region. In the kinetic region, the simultaneous integral equations for the flow velocity, density, and temperature are derived from the model equation. These equations are solved numerically by matching with the Oseen–Stokes solution. The distributions of the flow velocity are obtained for a wide range of the Knudsen numbers. The drag on the cylinder is also calculated and is favorably compared with the previous formulas valid for small and large Knudsen numbers. [ABSTRACT FROM AUTHOR]

Published
1985
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150. Flow of Rarefied Gas past a Circular Cylinder at Moderate Knudsen Numbers

Author

YAMAMOTO, Kyoji

Abstract

円柱を過ぎる希薄気体の遅い流れを, クヌーセン数が中程度の場合に, B-G-K方程式に基づいて解析している。分子は, 壁面で拡散反射されるとし, また, 円柱から十分離れたところで, 流れは, 連続体流に漸近するとして, B-G-K方程式から, 密度, 流速, 温度に対する連立の積分方程式を導びく。この方程式を, いくつかのクヌーセン数に対して数値的に解き, 密度, 流速等の分布, 及び, 円柱に働く抵抗を求めている。, The slow flow of rarefied gas past a circular cylinder at moderate Knudsen numbers is studied basig on the B-G-K equation. The equation is solved formally under the conditions that the molecule is reflected diffusely at the wall surface and that the flow tends asymptotically to the continuum one (Stokes-Oseen solution). The simultaneous integral equations for density, velocity and temperature are then derived and these are solved numerically for several values of the Knudsen number. The distributions of the mean quantities as well as the drag acting on the cylinder are obtained., 資料番号: SA0166537000

Published
1982

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