DSMC study of oxygen shockwaves based on high-fidelity vibrational relaxation and dissociation models

This work evaluates high-fidelity vibrational-translational (VT) energy relaxation and dissociation models for pure O-2 normal shockwave simulations with the direct simulation Monte Carlo (DSMC) method. The O-2-O collisions are described using ab initio state-specific relaxation and dissociation models. The Macheret-Fridman (MF) dissociation model is adapted to the DSMC framework by modifying the standard implementation of the total collision energy (TCE) model. The O-2-O-2 dissociation is modeled with this TCE+MF approach, which is calibrated with O-2-O ab initio data and experimental equilibrium dissociation rates. The O-2-O-2 vibrational relaxation is modeled via the Larsen-Borgnakke model, calibrated to experimental VT rates. All the present results are compared to experimental data and previous calculations available in the literature. It is found that, in general, the ab initio dissociation model is better than the TCE model at matching the shock experiments. Therefore, when available, efficient ab initio models are preferred over phenomenological models. We also show that the proposed TCE + MF formulation can be used to improve the standard TCE model results when ab initio data are not available or limited. Published by AIP Publishing.