Nozzle flows with coupled vibrational and dissociational nonequilibrium

Abstract : It was assumed that the vibrational state of the gas may be represented by a single vibrational temperature and that the effect of vibrational nonequilibrium on rates of dissociation may be taken into account by the introduction of a parameter which has the dimensions of temperature and which gives a higher probability for dissociation from higher vibrational energy levels. The dependence of this parameter on translational temperature is derived. However, in the calculations, an averaged constant value of this parameter is used as a simplification. The effect of dissociational nonequilibrium on vibrational relaxation is to modify the classical Landau-Teller equation by additional terms which take into account the average energy lost or gained due to dissociation and recombination. A qualitative study of the effects of the atom-molecule exchange reaction and relaxation from a higher to lower vibrationally excited state on the vibrational relaxation is carried out by shortening the vibrational relaxation times from those measured behind normal shocks. The analysis was successfully applied to predict the hypersonic nozzle test-section conditions for a newly developed UTIAS self-calibrating catalytic probe for measuring local atom concentrations in a dissociating oxygen flow. (Author)