Effect of blowing mass flux on porous mesostructure surfaproperties for hypersonic ablation

Exploration spacecraft require thermal protection systems (TPS) in order to survive hypersonic entry into an atmosphere. Many TPS are porous carbon fiber based materials that ablate and often involve material pyrolysis. One current research focus aims to provide uncertainty quantification and ensure reliability of such TPS systems, especially in regards to material failure. Such TPS materials often have complex micro and mesostructure (various fiber arrangements). This article presents numerical simulations (direct simulation Monte Carlo) of flight-relevant boundary layer flow over resolved material meso structure, and presents results for the heat flux, traction forces, and reactive atomic oxygen flux on the fiber surfaces. Instead of predicting single values for these properties at a macroscopic scale on the surface, the simulations predict probability distribution functions for these properties on the fiber surfaces. This information could be used in new stochastic models for material response and failure. This article presents boundary layer flow results that now include convection, diffusion, and simulated pyrolysis blowing effects. It is observed that the addition of a blowing gas slightly reduces the heat flux, traction, and atomic oxygen flux to the fiber surfaces, compared to simulations without a blowing gas. These reductions are quantified and distributions of these properties are analyzed.