Computational and Experimental Study of Nonequilibrium Flow in Plasma Wind Tunnel

The present work examines the thermochemical nonequilibrium flow in the freestream and shock layer of the Plasma Wind Tunnel Facility using experiments and computations. Computational studies were performed using the open-source solver hy2Foam, which was validated using the NASA Interaction Heating Facility case. Two chemical reaction models were used to compute the nonequilibrium state of air, composed of six species (N2, O2, NO, N, O, Ar). Optical emission spectroscopy was employed to experimentally capture the N2 first positive system emission from the freestream and molecular CN vibration bands emissions in the shock region. The Boltzmann plot method was employed to estimate the vibrational temperatures from the measured spectra. The measured vibrational temperatures in the freestream for two different transitions of N2 agree with one another, which shows that the vibrational modes obey the Boltzmann distribution for the conditions considered in this study. The vibrational temperatures computed using hy2Foam in the nozzle freestream and the shock layer for the Plasma Wind Tunnel conditions agree with the values obtained from optical emission spectroscopy.