ROTATIONAL AND VIBRATIONAL TEMPERATURE-MEASUREMENTS USING CARS IN A HYPERVELOCITY SHOCK LAYER FLOW AND COMPARISONS WITH CFD CALCULATIONS

Broadband single pulse coherent anti-Stokes Raman scattering (CARS) ex periments employing a folded-box phase-matching geometry in a pulsed h ypervelocity blunt body flow are presented. Rovibrational spectra of m olecular nitrogen, produced in the freestream and within the shock lay er at moderately high enthalpy (8.4 MJ/kg), are examined. Difficulties peculiar to the application of a single pulse optical technique to a high enthalpy pulsed flow facility are discussed and measurements of f low temperatures are presented. Theoretically calculated values for te mperatures based upon algorithms used to determine freestream and shoc k layer conditions agree well with experimental measurements using the CARS technique. The measurements indicate that thermal non-equilibriu m conditions exist within the freestream, and that near thermal equili brium exists at the point of measurement within the shock layer. The c omparison between the experiment and theory in the shock layer is impr oved by using the measured freestream temperatures as input to the sho ck layer computations.