Simulations of nonequilibrium reentry air plasmas by means of a collisional-radiative model

An accurate analysis of nonequilibrium air plasma flows is performed by using a one-dimensional shock-tube code. A collisional-radiative model accounts for thermal nonequilibrium between the translational and vibrational energy modes of individual molecular species and deals with electronic states of atoms as separate species. Therefore, non-Boltzmann distributions of the electronic state populations of atoms are allowed. Deviations from Boltzmann distributions are expected to occur in a rapidly ionizing regime behind a strong shock wave, depleting the high lying bound electronic states. In order to quantify the extent of departure from equilibrium of the electronic state populations, results are compared with those obtained assuming a Boltzmann distribution.