A CHEMICAL-EQUILIBRIUM METHOD FOR HYPERSONIC FLOW SIMULATIONS

In this paper, we report a new and efficient method to simulate high-s peed, chemically reacting flows with a chemical equilibrium model. Thi s computational method is based on the Helmholtz free-energy minimizat ion with two additional treatments to enhance computational efficiency . First, an estimation scheme for species compositions is implemented to either bypass the numerical iterations or significantly reduce them in the free-energy minimization procedure. Second, a frozen flow calc ulation method is adopted to take advantage of the non-reacting part o f the hypersonic flow field. In general, 95% of the full minimization procedure is avoided by using the two methods and no accuracy is sacri ficed in the final converged solution. In addition, the flow solver ad opted in the present study is incorporated with comprehensive, high te mperature, gas property models to simulate hypersonic flows and employ s an implicit, finite-volume, lower-upper (LU), time marching scheme t o solve flow equations in a fully coupled and very efficient manner. F inally, hypersonic internal flows under severe conditions are simulate d as numerical examples. The results are compared with those of a fini te-rate model, in which 11 species equations coupled with flow equatio ns are solved simultaneously. The results clearly depict differences i n the flow characteristics predicted by the two chemistry models.