HYPERSONIC NONEQUILIBRIUM-FLOW COMPUTATIONS USING THE ROE FLUX-DIFFERENCE SPLIT SCHEME

THE Roe flux difference splitting scheme is investigated for accuracy in simulating hypersonic reacting flows. The extension of the Roe sche me to include the finite rate chemical kinetic equations follows the a pproach of Grossman and Cinnella. Formal second-order accuracy is obta ined by employing the monotonic upstream schemes for conservation laws (MUSCL) approach in conjunction with the minmod limiter to degenerate the solution to first-order accuracy in the vicinity of strong shock waves. The full Navier-Stokes equations are solved with finite rate ch emistry for the flow past an axisymmetric blunt body at zero incidence at several Mach numbers. The vibrational energy is assumed to be in t hermodynamic equilibrium with the other internal energy modes. The air mixture is assumed to consist of the five species O2, O, N2, N, and N O. The surface heat transfer predicted by this scheme is validated for flows with Mach numbers 15.3 and 16.34 when compared with classical t heory and experimental results. Both catalytic and noncatalytic wall b oundary conditions are used. The entropy correction parameter, necessa ry to enforce the entropy condition in Roe's scheme, is found to be a simple and effective means to control numerical error due to the degen erated eigenvalue structure in the stagnation region, thus suppressing the numerical bulge or ''carbuncle'' phenomenon.