Rarefied gas flow simulation based on quasigasdynamic equations

Abstract

The treatment of rarefied gas flows by means of equations based on the mechanics of continuum media is desirable because solving such equations requires less computational resources than methods based on a molecular description. The present work aims at clarifying the domain of validity of two continuum approaches by comparing their results to a reference given by a direct simulation Monte Carlo method. The first continuum approach is based on the usual Navier-Stokes (NS) equations. The second one is based on the quasigasdynamic (QGD) equations that are derived from the Boltzmann equation. The present paper includes a self-consistent presentation of QGD equations. The flow along a flat plate has been considered for a freestream Mach number varying from 1.5 to 20 and a wall temperature taken successively equal to freestream and stagnation temperatures. The results suggest that the QGD equations are superior to the NS ones. A criterion is proposed for the validity of the continuum approaches.