Navier-Stokes Solutions with Finite Rate Ablation for Planetary Mission Earth Reentries

Abstract

A formulation of finite rate ablation surface boundary conditions, including oxidation, nitridation, and sublimation of carbonaceous material with pyrolysis gas injection, based on surface species mass conservation, has been developed. These surface boundary conditions are discretized and integrated with a Navier-Stokes solver. This numerical procedure can predict aerothermal heating, chemical species concentration, and carbonaceous material ablation rates over the heat-shield surface of reentry space vehicles. Two finite rate gas-surface interaction models, based on the work of Park and of Zhluktov and Abe, are considered. Three test cases are studied. The stream conditions of these test cases are typical for Earth reentry from a planetary mission with both oxygen and nitrogen fully or partially dissociated inside the shock layer. Predictions from both gas-surface interaction models are compared with those obtained by using chemical equilibrium ablation tables. Stagnation point convective heat fluxes predicted by using Park's finite rate model are usually below those obtained from chemical equilibrium tables and Zhluktov and Abe's model. Recession predictions from Zhluktov and Abe's model are usually lower than those obtained from Park's model and from chemical equilibrium tables. The effect of species mass diffusion on the predicted ablation rate is also examined.