Consistent multi-internal-temperatures models for nonequilibrium nozzle flows

A vibrational collisional model based on the database of the University of Bari is used to investigate non-equilibrium phenomena in nitrogen nozzle flows. For the cases studied, the vibrational distribution in the divergent section appeared to significantly deviate from a Boltzmann distribution. Multiquanta Vibration-Translation processes are shown to have a major influence on the recombination of the flow and on the shape of the vibrational distribution along the nozzle axis. Based on these results, a reduced model is derived with n groups of vibrational levels with their own internal temperatures to model the shape of the vibrational distribution. In this model, energy and chemistry source terms are calculated self-consistently from the rate coefficients of the vibrational database. For the studied nozzle flows, a good agreement is observed between the results of the vibrational collisional model with 68 levels and those of the reduced model with only 3 groups of levels.