Computational modeling of the flow environment in inductively coupled plasma jet facilities

The goals of this work are to evaluate under what conditions the flow in an inductively coupled plasma jet facility is in thermochemical equilibrium and to evaluate the accuracy of mapping subsonic ground based testing conditions to hypersonic fight. To accomplish this we use the US3D code in these different regimes, ensuring that identical thermal and chemical models are consistently applied to each case and accurate comparisons are drawn. Our simulations indicate that at lower operating pressures (2000 Pa), the flow upstream of the test article is in chemical nonequilibrium, while at higher pressures (10,000 Pa) the flow is very close to chemical equilibrium. The chemical nonequilibrium found at the low pressure condition is caused by molecular species diffusing towards the plasma jet core at a rate higher than the dissociation rate. At both high and low pressures, the flow in the jet upstream of the test article remains in thermal equilibrium, however, the flow within the boundary layer is found to be in thermal nonequilibrium. We find that for cases with perfect air, we are able to match the stagnation point heat ux of a subsonic flow over an axisymmetric probe with a hypersonic flow to within 7%. In a case where a spherical geometry is used in both subsonic and hypersonic cases, we are able to match the stagnation point heat flux within 1%. This indicates that the probe geometry may be important when considering which hypersonic conditions the ground based testing results represent.