Numerical study of the thermal response of high-temperature ablative materials

A theoretical model accounting for the effects of thermal nonequilibrium, temperature-dependent material properties, pyrotysis reaction, and thermochemical expansion is developed to predict the thermal response of high-temperature ablative materials when exposed to hyperthermal environments. The model, which is developed by using the volume-averaging and the finite volume techniques, is applied to predict the thermal response and the underlying heat transfer mechanisms of two typical ablative materials having distinctly different properties. From the numerical results, it is found that the method of mixture enthalpy leads to a better prediction of the thermal response than the method of mixture specific heat. It is also found that for an ablative material with relatively large permeability and porosity, the cooling effect of transpiration gases is significantly overpredicted by using the assumption of local thermal equilibrium.