Numerical investigation of the two-dimensional distribution of the population inversion and gain during supersonic expansion of a CO2–N2–He mixture

Results are presented of a numerical investigation of the flow of a vibrationally relaxing CO₂–N₂–He mixture during adiabatic expansion in planar and radial nozzles. Two-dimensional equations for the gasdynamics and relaxation kinetics, given in the form of integral conservation laws, are solved using a first-order explicit monotonic continuous counting scheme. Excitation of the optically active component on mixing with nitrogen is simulated in the instantaneous mixing approximation. Calculations are made of the gasdynamic channel of a radial nozzle grid with an annular diffuser. It is shown that the inversion density and gain are strongly dependent on the flow wave structure.