Collisional-radiative modeling in flow simulations

Overview & Synopsis

The present notes address the modeling of high speed re-entry plasma flows under strong nonequilibrium conditions. At high re-entry speeds, a significant portion of the heating experienced by the spacecraft can be due to radiation and it is highly influenced by the shape of the internal energy distribution function. In this notes, we propose a kinetic mechanism for air plasma under nonequilibrium conditions. We first analyze the behavior of the electronically excited state of the atoms in the post shock region during an high speed re-entry. The flight conditions are taken from FIRE II flight experiment and from the test conditions in the EAST shock tube facility. We move then to a more sophisticated model which accounts for non-boltzmann effects for electronic levels of atoms and molecules. Departure of the electronic energy level populations from Boltzmann distributions is found due to depletion of the high lying bound electronic states in the rapidly ionizing regime behind the strong shock wave.