Calculation by the Krylov-Bogolyubov method of the velocity profile and fluxes in the nonisothermal flow of a rarefied gas in a cylindrical capillary

1979 ◽  
Vol 13 (6) ◽  
pp. 906-911
Author(s):  
B. T. Porodnov ◽  
F. T. Tukhvetov
Keyword(s):  
Velocity Profile ◽  
Rarefied Gas ◽  
Nonisothermal Flow ◽  
Cylindrical Capillary ◽  
Bogolyubov Method

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.

scholarly journals Inverted velocity profile in the cylindrical Couette flow of a rarefied gas

2003 ◽  
Vol 68 (1) ◽  
Author(s):  
Kazuo Aoki ◽  
Hiroaki Yoshida ◽  
Toshiyuki Nakanishi ◽  
Alejandro L. Garcia
Keyword(s):  
Velocity Profile ◽  
Couette Flow ◽  
Rarefied Gas ◽  
Cylindrical Couette Flow

Investigation of the influence of the flow structure on the accuracy of flow measurement before a hydrometric structure in an open channel

2020 ◽  
pp. 41-44
Author(s):  
Anatoly Kusher
Keyword(s):  
Velocity Profile ◽  
Flow Velocity ◽  
Water Flow ◽  
Flow Measurement ◽  
Water Discharge ◽  
Critical Depth ◽  
Flow Measurements ◽  
Study Results ◽  
Flow Velocity Profile ◽  
Upstream Flow

The reliability of water flow measurement in irrigational canals depends on the measurement method and design features of the flow-measuring structure and the upstream flow velocity profile. The flow velocity profile is a function of the channel geometry and wall roughness. The article presents the study results of the influence of the upstream flow velocity profile on the discharge measurement accuracy. For this, the physical and numerical modeling of two structures was carried out: a critical depth flume and a hydrometric overfall in a rectangular channel. According to the data of numerical simulation of the critical depth flume with a uniform and parabolic (1/7) velocity profile in the upstream channel, the values of water discharge differ very little from the experimental values in the laboratory model with a similar geometry (δ < 2 %). In contrast to the critical depth flume, a change in the velocity profile only due to an increase in the height of the bottom roughness by 3 mm causes a decrease of the overfall discharge coefficient by 4…5 %. According to the results of the numerical and physical modeling, it was found that an increase of backwater by hydrometric structure reduces the influence of the upstream flow velocity profile and increases the reliability of water flow measurements.

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