Effects of gas models on hypersonic base flow calculations

Abstract

Numerical solutions for the Navier-Stokes equations are obtained for laminar, hypersonic flows around a flatbased projectile using perfect gas, equilibrium air, and nonequilibrium air models. The effects of different gas models are investigated for a freestream condition of Mach 20 at an altitude of 73 km. The species compositions for the equilibrium and nonequilibrium gases are obtained by minimizing the Helmholtz free energy and by solving species continuity equations, respectively. The chemical equations are combined with the gasdynamics equations using a loosely coupled technique. A finite volume method is implemented with the flux vector splitting of Steger and Warming for convective terms and centered differencing for viscous terms. Both explicit and implicit time integration schemes are used.