Book Description

A singular perturbation solution to the blunt-body stagnation-region flow of an inviscid, radiating gas has been obtained by means of the Poincař-Lighthill-Kuo, or perturbation-of-coordinates, method. A number of results for a gray gas have been presented in order to provide some physical insight into the effects of various parameters on the shock-layer enthalpy profiles and the radiant heat-transfer rates. A nongray absorption-coefficient model was developed which includes, in an approximate way, the important vacuum-ultraviolet contributions of bound-free and line transitions. This model was used to obtain solutions pertinent to the case of reentry into the earth's atmosphere. While the results are restricted to small values of the radiation cooling parameter, which characterizes the relative importance of radiation and convection as energy-transport mechanisms, they cover broad ranges of vehicle velocity, altitude, and nose radius, which are of practical interest. The characteristic enthalpy variation of the model absorption coefficient was found to be nearly independent of altitude and nose radius for fixed vehicle velocity except for velocities lower than 10.67 km/sec. Thus it was possible to correlate certain quantities by plotting these quantities as functions of the nondimensional adiabatic radiant heat-transfer rate for various altitudes and nose radii at fixed vehicle velocity. Among the quantities correlated was the cooling factor (the ratio of the stagnation-point radiant heat-transfer rate to the adiabatic radiant heat-transfer rate). The cooling-factor correlation is particularly useful because it eliminates the need to perform nonadiabatic calculations whenever radiant heat-transfer rates are desired. Also correlated was the factor by which the convective heat-transfer rate is reduced because of radiation losses in the shock layer. Finally, upper-bound estimates were made of the effects of absorption of precursor radiation by the free-stream air on the radiant and convective heat-transfer rates.