Simulations of Reactions Involving Charged Particles

During vehicle reentry into the Earth’s atmosphere from space, the flow field energy is sufficient to produce ionizing reactions. The weakly ionized plasma around the vehicle can interfere with vehicle communications, and in some cases can have an important effect on the rate of heat transfer to the capsule surface. In the present study, the modeling of reactions involving charged species is considered. Axisymmetric simulations of hypersonic flow about the forebody of the FIRE II reentry vehicle using the Direct Simulation Monte Carlo (DSMC) method are presented, with the flight conditions of the vehicle at 85 km altitude used as the test case. The baseline flow field solution is computed using the com-monly used Total Collision Energy (TCE) chemistry model to simulate reactions involving charged particles. The standard chemistry model is then replaced with both measured and computed cross section data for the simulation of electron impact ionization, associative ionization and dissociation of N2 by electron impact. The results obtained using the im-proved model are compared to those obtained with the baseline model, and the changes in the flow field variables are systematically examined. The use of reaction cross section data for modeling electron impact dissociation has a large effect on the computed flo