Convective instabilities in rarefied gases by direct simulation Monte Carlo method

Abstract

Benard and thermal stress instabilities in a rarefied gas are investigated by the direct simulation Monte Carlo (DSMC) method. Particular emphasis is given to the numerical aspects of DSMC (accuracy, convergence, etc.), that were not investigated in the previous studies and to the refining of the simulation results by using a special data processing (filtering) procedure. In the stratified rarefied gases with hightemperature gradients the Boussinesq approximation is not valid and it is shown that the onset of instabilities in the non-Boussinesq fluid (rarefied gas) is not determined by a single nondimensional parameter (Rayleigh number). Benard convection in the stratified rarefied gas is analyzed in different geometries, including the case with curvilinear boundaries. The occurrence of thermal stress convection in rarefied gases and in a continuum flow regime under zero gravity conditions was demonstrated using the DSMC method.