Modeling of NO radiation from unsteady and steady shocks using DSMC

Radiation of the NO gamma band emitted from nonequilibrium hypersonic bow shock flows in air has been studied for both unsteady one-dimensional reflected shock and steady flow over a cylinder cases and compared with experiments. The Larsen-Borgnakke model was used for internal energy relaxation and the total collision energy model is used with five chemical species (N₂, O₂, N, O and NO). The quasi-steady state (QSS) assumption was used in calculating the neutral-impact excitation of NO and the associated radiation. The calculated radiations are in good agreement with the experimental data of Gorelov for shock speeds below 7 km/s in the unsteady shock study. The calculated radiation is lower than the experimental data for even higher shock speeds. For the steady flow over a cylinder simulation, the shapes of the calculated scanned specific intensity profiles are in agreement with those of preliminary measured spectra in LENS-XX. The magnitudes of the calculated radiation along the line of sight to the stagnation point are about 1~2 orders of magnitude higher than the data and need to be studied further.