Spectroscopic Characterization of a Hypersonic Arcjet Flow

View Video Presentation: https://doi.org/10.2514/6.2023-3297.vid This study addresses the freestream characterization of the Mach 6 freestream tunnel of the University of Tennessee, using intrusive diagnostics. Stagnation point heat flux and Mach number were measured using a variety of different probes at a bulk enthalpy of 4 MJ/kg and a total pressure of 170 kPa. The heat flux was measured using two probes with flat and hemispherical geometry respectively, both instrumented with fast response coaxial thermocouples flush mounted at the stagnation point. The Mach number was evaluated from pitot pressure measurements using normal shock relations. Two pressure probes were used, one with sharp nose and one with blunt nose, both instrumented with piezoresistive pressure transducers. A two-dimensional motorized positioning system was built to scan multiple locations in the freestream and inside the nozzle. The heat flux and pressure at the stagnation point also allowed evaluating the local stagnation enthalpy of the freestream, using Sutton&Graves, and Fay&Riddell correlations, and compared it to the bulk enthalpy of the tunnel. Relatively uniform properties were found over a core region with a diameter of 50 mm where the stagnation enthalpies measured by the two probes were in good agreement with an average value of 7.3 MJ/kg.