Chemical and vibrational relaxation of an inviscid hypersonic flow

The conservation equations for an inviscid, nonconducting fluid with chemical and vibrational relaxation are put into characteristic form for the determination of hypersonic flow fields. Application of the analysis to the simpler case of vibrational equilibrium is also discussed. An approximation is presented wherein the nonequilibrium terms are considered along the streamline characteristics but are neglected along the Mach line. Results at typical entry conditions in the earth's atmosphere are determined for pointed bodies with and without vibrational equilibrium and for blunted bodies with vibrational equilibrium. The validity of this approximation is demonstrated by comparison with results of the corresponding exact calculation (i.e., with the nonequilibrium terms included in the Mach line relationships) for the blunt body in vibrational equilibrium. Comparisons are also made with results from frozen and equilibrium analyses. The effects of both chemical and vibrational relaxation, and variation of nose bluntness, on the downstream composition of the gas are shown to be appreciable. A comparison with results of a simpler one-dimensional, nonequilibrium stream tube analysis indicates that the latter is adequate in many cases.