Quasi-Classical Trajectory Modeling of OH Production in Direct Simulation Monte Carlo

The quasi-classical trajectory method enables one to obtain reaction probabilities and cross sections for fundamental reactions and to simulate strongly nonequilibrium flows. The formation of vibrationally hot OH for a rarefied flow about a sphere at 80- and 100-km altitudes are examined with 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 molecular dynamics (MD) code, we calculate the reaction cross sections and OH product rotational and vibrational distributions for two exchange reactions, H + O2 - > OH + O and O + H2 - > 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 + O2 exchange reaction is the main production mechanism of OH. Approximately an order of magnitude difference is observed for the MD and total collision energy rates, and differences in the predicted vibrational OH temperature were also obtained.