Evaluation of nonequilibrium boundary conditions for hypersonic rarefied gas flows

Department of Mechanical Engineering, University of Strathclyde, Glasgow G1 1XJ, United Kingdom

Abstract

A new Computational Fluid Dynamics (CFD) solver for high-speed viscous §ows in the OpenFOAM code is validated against published experimental data and Direct Simulation Monte Carlo (DSMC) results. The laminar §at plate and circular cylinder cases are studied for Mach numbers, Ma, ranging from 6 to 12.7, and with argon and nitrogen as working gases. Simulation results for the laminar §at plate cases show that the combination of accommodation coefficient values σ_u = 0.7 and σ_T = 1.0 in the Maxwell/Smoluchowski conditions, and the coefficient values A₁ = 1.5 and A2 = 1.0 in the second-order velocity slip condition, give best agreement with experimental data of surface pressure. The values σ_u = 0.7 and σ_T = 1.0 also give good agreement with DSMC data of surface pressure at the stagnation point in the circular cylinder case at Kn = 0.25. The Langmuir surface adsorption condition is also tested for the laminar §at plate case, but initial results were not as good as the Maxwell/Smoluchowski boundary conditions.