An energy bin based coupling model for recombination is derived for high enthalpy nozzle flows using oxygen as the test gas. The inherent coupling between vibrational and rotational modes is taken into account by the use of energy bins. A prior recombination distribution of molecules dependent on total energy available to a recombining system is obtained using information theory. The low lying electronically excited states of oxygen are also considered. The results from a state-specific model (Doraiswamy, S., Kelley J. D. and Candler G. V., "Analysis of Chemistry-Vibrational Coupling in High Enthalpy Nozzle Flows", AIAA-2010-1570, Jan. 2010) are used to compare against the results of the energy bin approach model. The energy bin approach using only the ground state of the oxygen molecule predicts similar conditions at the 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 non-trivial concentrations of the excited states. The effect of energy bias in the initial recombination distribution and the senstivity of the results to the rate constants are also investigated.
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