Application of Resonant Femtosecond Tagging Velocimetry in the 0.3-Meter Transonic Cryogenic Tunnel

Selective two-photon absorptive resonance femtosecond laser electronic excitation tagging (STARFLEET) velocimetry is demonstrated for the first time in a NASA Langley Research Center wind tunnel with high-repetition-rate and single-shot imaging. Experiments performed in the 0.3 m transonic cryogenic tunnel allowed for testing at 300 K in gaseous nitrogen over a range of pressures (124-517 kPa) and Mach numbers (0.2-0.8) for freestream conditions and flow behind a cylindrical model. Measurement precision and accuracy are determined for the current set of experiments, as are signal intensity and lifetime. Precisions of 3-5m/s (based on one standard deviation) were typical in the experiment; precisions better than 2% of the mean velocity were obtained for some of the highest-velocity conditions. Agreement within a mean error of 3m/s between STARFLEET freestream velocity measurements and facility data acquisition system readings is demonstrated. STARFLEET is also shown to return spatially resolved velocity profiles, although some binning of the signal is required to achieve the reported measurement precision.