SPATIAL NONHOMOGENEITY EFFECTS IN NONEQUILIBRIUM VIBRATIONAL KINETICS

The paper addresses several problems of kinetics of spatially nonhomogeneous, vibrationally excited gas flows. It is shown that vibrational energy transfer in most diatomic molecules does not affect the transport coefficients of a gas, despite very fast vibration-to-vibration (V-V) rates among high vibrational levels. The influence of diffusion and the vibration-to-electronic (V-E) energy transfer on the vibrational distribution function (VDF) and on the vibrational energy balance is discussed. The diffusion and V-E corrections to the VDF and to the gas heating rate in vibrational relaxation is obtained for the ''strong'' excitation regime. The effect of the non-local diagnostics on the VDF is considered. It is shown that the spatial integration may significantly influence the inferred distribution function, as has been previously reported in experiments. A new approach for kinetic modeling of nonhomogeneous, vibrationally nonequilibrium flows is suggested. A two-dimensional kinetic model is developed which combines vibrational and translational energy balance and gas motion equations with the analytical theory of anharmonic oscillators. The comparison of the model calculations with both 1D and 2D experiments shows reasonable agreement within the applicability of the gas flow model.