Asymptotic Behavior of Diffusion of Tangential Velocity Discontinuity in Rarefied Gas

1968 ◽  
Vol 11 (9) ◽  
pp. 1935 ◽  
Author(s):  
Yoshio Sone
Keyword(s):  
Asymptotic Behavior ◽  
Rarefied Gas ◽  
Tangential Velocity ◽  
Velocity Discontinuity

Cylindrical Couette Flow of a Rarefied Gas From Macro- to Micro-Scales

2009 ◽  
Author(s):  
Sheng Wang ◽  
Kangbin Lei ◽  
Xilian Luo ◽  
Kiwamu Kase ◽  
Elia Merzari ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Velocity Profile ◽  
Couette Flow ◽  
Knudsen Number ◽  
Rarefied Gas ◽  
Outer Cylinder ◽  
Tangential Velocity ◽  
Flow Field Characteristics ◽  
Dimensional Parameters

The cylindrical Couette flow of a rarefied gas from macro- to micro-scales, in the case where the inner cylinder is rotating whereas the outer cylinder is at rest, is extensively investigated by direct simulation Monte Carlo (DSMC) code incorporated with a Volume-CAD software. The generalized soft sphere (GSS) model is applied to an intermolecular collision calculation. The diffuse reflection model and Cercignani-Lampis-Lord (CLL) model are used to model the molecule-surface interaction by considering the accommodation coefficients on inner cylinder (ACI hereafter) and outer cylinder (ACO hereafter) separately. The contents in this paper include following three aspects: I the flow field characteristics and force and torque on inner cylinder for eccentric Couette flow between different scales with same non-dimensional parameters (accommodation coefficients, eccentricity-clearance ratio, Knudsen number and Reynolds number) are compared; the flow field characteristics for different scales are same; with the increase of the scale, the total force on the inner cylinder increases slightly, while the torque is proportional to the scale; II the velocity profiles in concentric Couette flow under different non-dimensional parameters are studied; the result shows that the phenomenon of inverted velocity profile in the concentric Couette flow is only induced by a smooth outer cylinder; the non-dimensional tangential velocity, as well as its gradient is high at low Reynolds number; the Knudsen number has great impact on the tangential velocity profile, and the velocity profile may not be inverted in the case of low Knudsen number; III the flow field characteristics in eccentric Couette flow under different non-dimensional parameters are obtained; the recirculation zone may not appear when Knudsen number is high; the position of its center may be different depending on Reynolds number; with the increase of Reynolds number, the compressibility effect becomes important; stratified distribution of the density becomes obvious at low Knudsen number.

Slipping stream instability in anisotropic plasma with magnetic shear

1968 ◽  
Vol 2 (2) ◽  
pp. 181-187 ◽  
Author(s):  
S. S. Rao ◽  
G. L. Kalra ◽  
S. P. Talwar
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Tangential Velocity ◽  
Anisotropic Plasma ◽  
The Other ◽  
Magnetic Shear ◽  
Velocity Discontinuity ◽  
Special Case ◽  
The Magnetic Field ◽  
Stream Instability

Starting with the Chew, Goldberger & Low equations, an analysis is made of instability arising due to a tangential velocity discontinuity in a dilute plasma. The velocities on either side are parallel but oppositely directed. Two cases are considered: (i) the magnetic field is uniform and everywhere transverse to the motion, and (ii) the magnetic field vectors on either side are orthogonal, being parallel to the motion on one side and perpendicular on the other. The conditions for instability are obtained and it is found that the effect of magnetic field is destabilizing in both cases. The effect of orthogonality of magnetic fields on the conventional fire-hose instability for a uniform, static plasma is also discussed as special case.

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