Treatment of the Thermal Nonequilibrium and Ionization Effects on the Refractive Index of a Reacting Gas: Atmospheric Air and Combustion Products

Using thermal nonequilibrium physicochemical kinetics models, which make it possible to numerically study the reacting gas flows with allowance for the processes of vibrational and electronic-translational relaxation and exchange, as well as the chemical and plasmachemical reactions, the profiles of the Gladstone–Dale constant and refractive index are calculated for two model problems: relaxation of the air behind the shock wave (SW) front and expansion of hydrogen and syngas combustion products in a supersonic nozzle. The required data on the electrical properties (polarizability and dipole moment) of the neutral and charged gas components in their ground and excited states are taken from the literature or estimated using recently developed analytical models. For each of the model gas-dynamic problems, the accuracy of various approximations when calculating the optical properties of a gas is analyzed.