Reactive and nonreactive vibrational energy exchanges in nonequilibrium hypersonic flows

Abstract

The generalized depletion equations, considering state-to-state kinetics of dissociating nitrogen, were solved to predict the extent of vibrational depletion for 4000 and 6000 K. Two different vibrational transition rate sets were used in the depletion analysis. One was based on the Schwartz–Slawsky–Herzfeld (SSH) theory and the other based on the analytical methods of Capitelli, Billing, Fisher, Doroshenko and co-workers. Transition rates based on the SSH theory predicted a lower depletion due to very high rates in the upper levels. With the objective of delineating the vibration–vibration (V–V) exchanges and vibration–translation (V–T) transfers in nonreactive, vibrationally excited gas dynamic flows, the flowfield simulations of blunt body and expanding nozzles were performed. For vibrational cooling cases (where vibrational temperature is greater than translational temperature) of flow past blunt body and the nozzle flows, the population distribution showed the Treanor-like distribution only at low translational temperatures. This non-Boltzmann behavior and the corresponding low state densities establish the dominance of the V–T energy transfers and the relatively minor role of V–V exchanges for hypersonic gasdynamic flows.