Numerical study of the accommodation coefficient influence on rarefied gas flow through a microchannel

Abstract

In this paper, the influence of the tangential momentum accommodation coefficient αv (TMAC) on an assumed planar, compressible, and slightly rarefied nitrogen gas flow through a microchannel was numerically investigated. Given the small values of Knudsen numbers (0.04<Kn<0.07) and the low Mach number (Ma<0.3), the 2D governing equations were solved using the finite element method with first-order slip boundary conditions using the COMSOL Multiphysics software. The obtained results were presented and discussed. Those results are in good agreement compared to analytical solutions and to the DSMC results obtained by the literature, which confirms the validity of the present model. A comparison with experimental data provided from the literature for pressure distribution of airflow through a long microchannel was also presented and comparable results were found. It has been proved that COMSOL is faster in resolving such problems compared to DSMC method. It has been shown that decreasing the tangential momentum accommodation coefficient αv values increases the gas velocity and the velocity jump near walls, while the pressure gradient is reduced for the given αv values. It has been also shown that for tending to zero values of αv, vortices in the inlet chamber become more intense.