Investigation of Post-Shock Fluctuation Levels in Non-Equilibrium Hypersonic Flow Conditions

Abstract: A modified cylindrical focused laser differential interferometer was utilised to quantify density fluctuations in the freestream and post-shock for air and nitrogen test flows around a blunted, flat plate. Experiments were conducted in the T4 Stalker Tube. The plate had a 5mm leading edge radius and was inclined at 10 degrees to the oncoming flow. The total enthalpy of the flows was approximately 10 MJkg ^(-1) where non-equilibrium turbulence-chemistry interactions are pronounced. The shock-standoff distance was found to be larger for nitrogen than for air. Post-shock fluctuation levels were higher than in the freestream for both gases, with nitrogen showing higher fluctuations at both probing locations. The differences are attributed to non-equilibrium effects and different boundary layer transition locations along the nozzle for the two gases. Keywords: Cylindrical focused laser differential interferometer, density fluctuations, turbulence chemistry interactions, non-equilibrium or high-enthalpy hypersonic flows, shock tunnel experiments