Picosecond-laser-electronic-excitation (PEET), a non-intrusive seedless velocimetry technique, is demonstrated in an AFRL Mach-6 Ludwieg tube at repetition rate of 100 kHz employing a 1064-nm, 100 ps, burst-mode laser. The system performance for high-speed velocimetry in unseeded air and nitrogen Mach-6 flows at a very-low static pressure range of 8-20 torr was evaluated. Time-resolved PLEET velocity measurements were performed in freestream and with a 14-degree cone model. Based on freestream flow measurement and computational fluid dynamics (CFD) calculation, we conclude that the measurement uncertainty of 100-kHz PLEET measurement for Mach 6 flow is less than 1%. The measured velocity profdes for model case also showed good agreement with CFD calculation before shock wave. Behind the Shockwave, the observed discrepancy between CFD and experimental measurement could attribute to the fluctuation of the cone model attacking angle during the experiment. Our results showed promise for utilizing 100-kHz PLEET velocimetry to understand real-time dynamics of turbulent hypersonic flows and provide capability to collect sufficient data in fewer test run in real hypersonic facilities.
展开▼
