Accurate Freestream Characterization in Inductively Coupled Plasma Flows for Testing Reentry Conditions

A procedure combining optical emission spectroscopy measurements and one-dimensional stagnation-line computations has been introduced, demonstrating that experimental observations align with boundary-layer simulations over a spectrum of Plasmatron operating conditions. This study focuses on a critical aspect of the procedure, specifically the choice of inlet boundary conditions used in the numerical simulations, and extends the methodology to a broader set of test conditions, covering most of the Plasmatron testing envelope in the subsonic regime. The results indicate that defining the inlet at six times the probe radius (6R) from the probe location, while imposing the temperature measured at 0.4R and the velocity measured at 0R, provides an optimal balance. The procedure is then applied to test cases that span chamber pressures from 200 to 15 mbar and input powers from 150 to 300 kW. The resulting freestream parameters range from 5400 to 8600 K in temperature, [Formula: see text] in enthalpy, and [Formula: see text] in velocity gradient. Additionally, a comparison between experimental and numerical heat fluxes provides a rough estimate of the surface recombination coefficient for copper oxide, which is found to be approximately 1 for the 100 and 200 mbar cases, and between 0.02 and 0.03 for the lower-pressure conditions.