Navier Stokes Simulations of Hypersonic Flows with Coupled Graphite Ablation

摘要

A study of graphite ablation in reentry flows is carried out by a surface ablation approach integrated with a two-ndimensional axisymmetric Navier–Stokes solver. The gas–surface interaction model is based on chemicalnequilibriumablationwith surfacemass and energy balances fully coupled with the numerical solver and can accountnfor both surface oxidation and sublimation. The surface temperature is obtained from the steady-state ablationnapproximation. This numerical procedure can predict aerothermal heating, chemical species concentrations, andncarbon material ablation rate over the heat-shield surface of reentry vehicles. Two-dimensional axisymmetricnsimulations have been performed to numerically reproduce the ablation of a graphite sphere cone that has beenntested in the Interaction Heating Facility at the NASA Ames Research Center. The freestream conditions of thenselected test case are typical for Earth reentry from a planetary mission. The predicted ablation rate and surfacentemperature assuming frozen chemistry in the flowshowa good agreementwith the available experimental data.Thenagreement is further improved freezing the nitrogen recombination reaction at the surface to bemore consistentwithnexperimental observation, which has shown nitrogen atom recombination not to occur at the graphite surface.