scholarly journals Correction to: Rarefied gas effect in hypersonic shear flows

2021 ◽  
Author(s):  
Jie Chen ◽  
Heng Zhou
Keyword(s):  
Shear Flows ◽  
Rarefied Gas ◽  
Rarefied Gas Effect ◽  
Gas Effect

Rarefied gas effect in hypersonic shear flows

2021 ◽  
Vol 37 (1) ◽  
pp. 2-17
Author(s):  
Jie Chen ◽  
Heng Zhou
Keyword(s):  
Shear Flows ◽  
Rarefied Gas ◽  
Rarefied Gas Effect ◽  
Gas Effect

scholarly journals Simulation of Gas Flow Over a Micro Cylinder

2009 ◽  
Author(s):  
Yuan Hu ◽  
Quanhua Sun ◽  
Jing Fan
Keyword(s):  
Reynolds Number ◽  
Mach Number ◽  
Drag Coefficient ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Low Reynolds Number ◽  
Pressure Drag ◽  
Low Reynolds ◽  
Rarefied Gas Effect ◽  
Gas Effect

Gas flow over a micro cylinder is simulated using both a compressible Navier-Stokes solver and a hybrid continuum/particle approach. The micro cylinder flow has low Reynolds number because of the small length scale and the low speed, which also indicates that the rarefied gas effect exists in the flow. A cylinder having a diameter of 20 microns is simulated under several flow conditions where the Reynolds number ranges from 2 to 50 and the Mach number varies from 0.1 to 0.8. It is found that the low Reynolds number flow can be compressible even when the Mach number is less than 0.3, and the drag coefficient of the cylinder increases when the Reynolds number decreases. The compressible effect will increase the pressure drag coefficient although the friction coefficient remains nearly unchanged. The rarefied gas effect will reduce both the friction and pressure drag coefficients, and the vortex in the flow may be shrunk or even disappear.

Analysis and Comparison of the Models for the Rarefied Gas Effect on Gas Lubrication

2014 ◽  
Vol 577 ◽  
pp. 289-292
Author(s):  
Shuai Zhang ◽  
Peng Yun Song
Keyword(s):  
Knudsen Number ◽  
Flow Rate ◽  
Dynamic Viscosity ◽  
Effective Viscosity ◽  
Rarefied Gas ◽  
Viscosity Coefficients ◽  
Gas Lubrication ◽  
Rarefied Gas Effect ◽  
Gas Effect ◽  
Inverse Knudsen Number

Ultrathin gas film lubrication has been widely used in recent years, such as dry gas seal face gas lubrication, gas lubrication in the hard disk drive, etc. The rarefied gas effect must be considered when the gas film thickness is very thin. In order to analyze, compare, and select the appropriate rarefied effect model on gas lubrication, a comparative analysis has been carried out on the influence laws of the Poiseuille flow rate and the ratio of the effective viscosity coefficients and the dynamic viscosity, μeff/μ, with inverse Knudsen number, D ,or Knudsen number, Kn, as to different models. The results show that when inverse Knudsen number increases or Knudsen number decreases, the Poiseuille flow rate and the ratio of the effective viscosity coefficients and the dynamic viscosity,μeff/μ, of different models approach to each other. However, there are significant differences as to different models when the Knudsen number is large, and only several models from Hwang, Veijola, Peng etc agree with Fukui’s model.

Study of Temperature and Velocity Distribution of Rarefied Gas Flow in Micro-Nano Channels

2009 ◽  
Author(s):  
Hadi Ghezel Sofloo ◽  
Alireza Shams ◽  
Reza Ebrahimi
Keyword(s):  
Heat Transfer ◽  
Gas Flow ◽  
Rarefied Gas ◽  
Direct Simulation Monte Carlo ◽  
Ideal Gas ◽  
Gas Density ◽  
Channel Size ◽  
Flow And Heat Transfer ◽  
Nonideal Gas ◽  
Gas Effect

This paper deals with simulation of transport phenomena in micro and nano pores. The number of cavities and the cavity radius were estimated by using Henry’s law for adsorption of Argon onto ZSM-5 and NaX zeolites. This work showed both of zeolites have pores with average size less than 1 nm. Then with using micro-nano channel assumption instead of micro-nano pores, gas flow and heat transfer were investigated. Subsonic nonideal gas flow and heat transfer for different Knudsen number are investigated numerically using the Direct Simulation Monte Carlo method modified with a consistent Boltzamnn algorithm. The collision rate is also modified based on the Enskog theory for dense gas. It is shown that nonideal gas effect becomes significant when the gas becomes so dense that the ideal gas assumption breaks down. The results also show that the nonideal gas effect is dependent not only on the gas density, but also the channel size. A higher gas density and a smaller channel size lead to a more significant nonideal gas effect. The nonideal gas effect also causes lower skin friction coefficients and different heat transfer flux distributions at the wall surface.

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