Vibrational–translational energy exchange models for the direct simulation Monte Carlo method | CU Experts

The model which controls the distribution of energy among the different molecular modes is a crucial component of accurate simulation of nonequilibrium rarefied flows. Two new models for the direct simulation Monte Carlo method that govern energy redistribution between the translational and vibrational modes are presented here. The first model is a modified form of the phenomenological Borgnakke–Larsen model. The probability of inelastic collision is evaluated using the relative velocity of collision. The second energy exchange model considered in this study is the multiple quantum-step transition model. The process of vibrational relaxation occurs through transitions between the different energy levels, allowing jumps of more than one level. Probabilities of activation and deactivation which depend on the relative velocity are used here. The new models are compared with existing schemes for several conditions. Significant differences are found for the vibrational energy distribution function computed in a hypersonic bow-shock wave.

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