Velocity measurements in a hypersonic flow using acetone molecular tagging velocimetry.

In the present work, a non-intrusive diagnostic technique known as molecular tagging velocimetry was used to collect quantitative freestream velocity measurements in the Mach 7 Ludwieg Tube Wind Tunnel located at The University of Texas at San Antonio. This laser-based diagnostic technique used a single Nd:YAG 4th harmonic laserline to excite acetone molecules seeded in the flow field. From the resulting emitted light, mean and instantaneous velocity profiles in the hypersonic freestream flow and facility boundary layer were measured. Uncertainty in the velocity measurements for individual test runs is estimated at ≤ 8% while overall 1D freestream mean velocity measurements were recorded with ±2.4% (± 21 m/s) accuracy. The effect of acetone seeding on the speed of sound was also quantified.

Naphthalene laser-induced fluorescence measurements at low temperature and pressure.

Few studies on naphthalene vapor fluorescence have been conducted at low temperature and pressure conditions. The current study focuses on conducting measurements of naphthalene quenching and absorption cross section in a temperature- and pressure-regulated test cell with 266 nm laser excitation. The test-cell measurements were of the naphthalene-fluorescence lifetime and integrated fluorescence signal over the temperature range of 100 to 525 K and pressure range of 1 to 40 kPa in air. These data enabled the calculation of naphthalene-fluorescence quantum yield and absorption cross section over the range of temperatures and pressures tested, which were then fit to simple functional forms for future use in the calibration of naphthalene laser-induced fluorescence (LIF) measurements. Furthermore, the variation of naphthalene-fluorescence signal with respect to temperature was investigated for four different excitation wavelengths, demonstrating that a two-line naphthalene LIF thermometry technique may be feasible.