Use of Quasi-classical trajectory methods in the modeling of OH production mechanisms in DSMC

The Quasiclassical trajectory (QCT) method enables one to obtain reaction probabilities and cross sections for fundamental reactions and to simulate strongly non-equilibrium flows. We examine the formation of vibrationally hot OH for a rarefied flow about a sphere at 80 and 100 km altitudes using the direct simulation Monte Carlo (DSMC) method. The main objective is to apply new chemistry models in the DSMC simulations of OH formation mechanisms in hypersonic flows at high altitudes. Using a numerically efficient parallel MD code, we calculate the reaction cross sections and OH product rotational and vibrationsl distributions for two exchange reactions, H + O ₂ → OH + O and O + H ₂ → OH + H. The reaction probabilities are then used in a DSMC computational tool to study OH production at 80 and 100 km altitudes. It is found that at 100 km the H+O ₂ exchange reaction is the main production mechanism of OH. Approximately an order of magnitude difference is observed for the MD and TCE rates, and differences in the predicted vibrational OH temperature were also obtained.