Approximations for nonequilibrium hypervelocity aerodynamics

The exponential term in the expression for the forward reaction rate in a nonequilibrium dissociating gas has been exploited to produce three simplified, approximate concepts that assist in understanding the effects of nonequilibrium in hypervelocity flows. The concepts are as follows: a constant-temperature approximation, the thermodynaniic decoupling of the temperature, and pressure-gradient reaction quenching. These concepts are seen to allow satisfactory prediction of shock standoff on a sphere, the growth of shock detachment on a wedge, the variation of shock standoff on a delta wing, and the shock-layer density profile downstream of a curved shock. The mechanism underlying the constant-temperature approximation also makes it possible to develop a second-order theory of nearly constant-pressure flows, which is used to predict the nonequilibrium center-of-pressure shift on wedges and delta wings