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 4^th 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.