Gas Dynamics with Nonequilibrium Radiative and Collisional Ionization

Abstract

The dynamics of a gas undergoing nonequilibrium ionization by both radiative (bound-free) and collisional transitions is formulated. Examination of the theory leads to a number of general deductions. The ionization rates and emission and absorption coefficients are all evaluated explicitly from statistical results available for the monatomic gas considered. This makes the problem concrete; one also sees that the approach for other cross sections, transitions, and gases would be analogous in most or many respects. It is shown that spectral complexities can sometimes be removed by expansion in terms of a large thermal parameter, and there emerges rationally a gas which is approximately gray above the edge frequency. The general theory is applied to the strong normal shock wave structured by the nonequilibrium ionization processes. The nature of this problem is examined, the complete structure is computed, the photoionization in the precursor portion of the shock structure is also determined according to the black-body emitter model for comparison, and the spectral as well as a directional approximation are assessed.