Transparency assumption in hypersonic radiative gas dynamics

Abstract

A detailed analytical investigation is presented of the influence of radiant energy transport 011 the structure of the inviscid flow field in the stagnation region of a blunt body in hypersonic flight. It is shown that the classical condition of small characteristic optical depth is not sufficient to justify neglecting self-absorption in flows with strong radiation. The omission of self-absorpti on terms leads to a qualitatively incorrect description of inviscid flow temperature and density distributions in the strongly cooled region near the body streamline and results in a zero temperature at this streamline. The inclusion of self-absorption eliminates these anomalous behavior characteristics. A second-order approximate solution is given which includes at each point local self-absorption of radiation emitted by hotter gas in the neighborhood of the point. This solution exhibits a reasonable physical behavior throughout the flow field and predicts that gas temperature approaches a well-defined nonzero value at the body surface. This provides an enthalpy potential for convective surface heat transfer in flow regimes where viscous effects are confined to a thin boundary layer. Direct estimates are thus obtained of the influence of radiation energy transport on both radiative arid convective heat transfer.