Abstract
AplanarDoppler velocimetry (PDV) systemwas developedand demonstrated in a small-scale facility (Mach 1.36 freejet) and then applied in a large-scale subsonic wind tunnel, where measurements were made over a delta wing at a 23-deg angle of attack. This PDV system utilized a pulsed, injection-seeded, frequency-doubled Nd:YAG laser to interrogate the ow. Back-illuminatedcharge-coupled device (CCD) cameras in conjunctionwith an iodine lter were used to record imagesproducedby the scattered laser light,permittingthedeterminationof the velocity at each CCD pixel. The PDV instrument also included custom software and a frequency-monitoring system composed of photodiodes,gated integrators, anda second iodinecell.With this setup, we recorded the shot-to-shot iodine- ltered and reference images and the associated laser frequency. In the freejet, mean velocities in the core were measured by PDV to within 6.4 m/s (out of » 260m/s) of the value obtainedby laser Doppler velocimetry. In the wind tunnel, freestream empty-tunnel measurements indicated bias and random errors of less than 2 and 4 m/s, respectively. The dominant source of random error arose from laser speckle, and the dominant source of bias error came from the characterization of the iodine lters. Measurements over the delta wing showed similar velocity ranges but smaller vortex cores when compared to the velocity eld predicted by a computational uid dynamicsmodel.
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