Investigation of non-Boltzmann distribution in hypersonic nozzle flows of nitrogen

Abstract: This work quantitatively estimates the effects of non-Boltzmann distribution in hypersonic nozzle flows of nitrogen. An entropy measure is used to quantify the extent of nonequilibrium. We apply this measure to a CFD simulation using a vibrationally-specific model of an experimental nozzle flow of nitrogen reported in the literature using Eilmer, a compressible flow software developed in The University of Queensland. As a comparison, a simulation is also completed using a Boltzmann model. The results give a quantitative view of how much the nozzle flow deviates from Boltzmann distribution, and whether modelling with Boltzmann distribution under this condition is reasonable. Results indicate that the Boltzmann distribution assumption is valid for the case investigated. Keywords: Thermal nonequilibrium, State-specific modelling, Non-Boltzmann distribution, Expansion flow