Energy bin model for high-enthalpy flows using prior recombination distribution

An energy-bin-based coupling model for recombination is derived for high-enthalpy nozzle flows using oxygen as the test gas. The coupling between vibrational and rotational modes is taken into account by the use of energy bins. A prior recombination distribution of molecules, dependent on the total energy available to a recombining system, is obtained using information theory. The low-lying electronically excited states of oxygen are also considered. The energy levels are obtained assuming the oxygen molecules behave as Morse oscillators. The results from a statespecific model are used to compare with the energy-bin approach. The energy-bin approach using only the ground state of the oxygen molecule predicts similar conditions at the nozzle test section as the state-specific model. The inclusion of the excited electronic states in the energy-bin approach calculations produces test section conditions with significant chemical nonequilibrium and also predicts nontrivial concentrations of the electronically excited states. The effect of energy bias in the initial recombination distribution and the sensitivity of the test section conditions to the interbin rate constants are also investigated.