Collisional-Radiative Modeling Behind Shock Waves in Nitrogen
Résumé
Nonequilibrium plasma, produced by the propagation of a shock wave in a shock tube or behind a shock front detached from a body entering a planetary atmosphere, requires the development of state-to-state models. The collisional-radiative model for N2 has been elaborated on in this framework for pure nitrogen flows. Its elaboration is reported in this paper. The model includes N2, N+2, N, N+, and free electrons in thermochemical nonequilibrium. The model is vibrationally and electronically specific insofar as the vibrational states of the electronic ground state of N2 and the electronic excited states of N2; and the electronic ground and excited states of N+2, N, and N+ are individually treated. These states are involved in collisional and radiative elementary processes, forming a set of around 40,000 basic data. This model is implemented in a one-dimensional flow, numerical code based on an Eulerian approach. Two test cases are treated at Mach numbers of around 30 and 40, the conditions of which relate to the reentry experiment of the Flight Investigation of Reentry Environment II probe. The behavior of the species on their different states is described in detail. It is shown that the vibrational distribution departs from the Boltzmann equilibrium. The global dissociation and ionization phases of the flow are examined by analyzing the source term for N ground state and electron densities. The radiative losses do not play a significant role in the present conditions.
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