Multidimensional Gas Flow Through Permeable Char Layers and Its Effects on Ablation

Résumé du livre

A theoretical analysis of the pressure fields within the char layers of cylindrical and hemispherical ablation models is presented. The distribution over the surface of mass flow from the char layer is given for both geometries. These multidimensional mass-flow distributions show that gas flow through the char layer can be significantly different from the one-dimensional assumption previously used by ablation analysts. Further, the theoretical results show that it is possible for the external pressure field to cause gas flow into the char layer, in which case the diffusion of energy and oxygen through the boundary layer to the material surface is increased. The appropriate analytical results were used to modify an existing one-dimensional ablation computer program to make convective blocking at the ablator surface responsive to the major parameters governing mass flow through permeable char layers. A comparison of analytical and experimental results shows that ablation performance can be significantly affected by multidimensional mass flow through the char layer.