Development of an impulsive model of dissociation in direct simulation Monte Carlo

Abstract

A previously proposed classical impulsive model for dissociation of diatomic molecules in direct simulation Monte Carlo (DSMC), the Macheret-Fridman for direct simulation Monte Carlo (MF-DSMC) model [Luo et al., “Classical impulsive model for dissociation of diatomic molecules in direct simulation Monte Carlo,” Phys. Rev. Fluids 3, 113401 (2018)], is extended in this work. To improve the prediction of state-specific rates at high vibrational energy, the anharmonic vibrational phase angle distribution function is first incorporated into the model. Then, to improve the prediction of thermal equilibrium dissociation rates, the general concept of calculating total collision cross sections with the MF-DSMC model is discussed and the framework of implementing a collision model based on exponential potential is constructed. The improved model is validated by comparisons with quasiclassical trajectory calculations, empirical estimations, and experimental measurements. In general, better agreement compared with the original version of the model is obtained. The improved model is also evaluated by simulating O2 reacting shock experiment.