Application of Reflected Shock Wave Configuration to Validate Nonequilibrium Models of Reacting Air

Abstract

The direct simulation Monte Carlo (DSMC) method is used to model transient thermal and chemical relaxation behind reflected shock waves in oxygen–argon and air mixtures under conditions reproducing earlier shock-tube experiments. Two vibration–translation and three popular DSMC chemical reaction models are tested. Where possible, model parameters are adjusted to match equilibrium and nonequilibrium [Formula: see text] relaxation times and reaction rates. A number of factors that impact relaxation and reaction model validation are examined, including gas–surface interactions, time-varying freestream properties, location of the observation point, electronic excitation, and nonequilibrium populations of vibrational states probed in the experiments. Comparison of numerical and experimental results has demonstrated that the reflected shock configuration is a platform very convenient for validation and analysis of high-temperature chemical reaction models. Computations have shown that the Bias reaction model is superior to the total collision energy and quantum kinetic models, providing reasonable agreement with measured absorbance time histories and [Formula: see text] vibrational temperatures in oxygen–argon mixtures and pure [Formula: see text]. There are some modeling-versus-experiment differences observed for air that may warrant additional studies focused on Zeldovich reaction rates and oxygen–nitrogen vibrational excitation and nonequilibrium dissociation rate.