Simulation of Oxygen Chemical Kinetics Behind Incident and Reflected Shocks via Master Equation

Abstract

A model for simulating postshock conditions using only state-resolved kinetic data of ab initio accuracy is presented. The quasi-classical trajectory method is used to compute a vibrational-specific kinetic database that describes internal energy transfer and dissociation in a nonionizing oxygen mixture. The kinetic database is implemented in a system of master equations and coupled to conservation laws to simulate a series of conditions, including zero-dimensional adiabatic reservoir, one-dimensional postincident, and one-dimensional postreflected shock relaxation. The present results are in excellent agreement with temperature profiles produced by the direct molecular simulation method at a fraction of cost. For the first time, the state-resolved model is applied to model relaxation behind a reflected shock passing through a thermally nonequilibrium gas. Model validation is made via comparisons to the experiments of Ibraguimova et al. (Journal of Chemical Physics, Vol. 139, No. 3, 2013, Paper 034317) and Streicher et al. (Physics of Fluids, Vol. 33, No. 5, 2021, Paper 056107). It is shown that neglecting relaxation in the postincident shock region may lead to nonnegligible errors in determining initial postreflected shock translational and vibrational temperatures, particularly in cases where the test gas is not diluted with an inert species.