Hybrid Pulse-Burst / Cross-Correlation DGV For High-Speed Flow Measurements At 100 KHz

Hybrid pulse-burst Doppler global velocimetry (PB-DGV)/pulse-burst, cross-correlation DGV (PB-CC-DGV) was demonstrated for the first time in the NASA Langley 4-foot Supersonic Unitary Plan Wind Tunnel, allowing simultaneous acquisition of mean and instantaneous high-repetition-rate velocity fields. The technique was used to make planar velocity measurements across an oblique shockwave generated by a large splitter plate set at a -2° angle of attack in a Mach 2.4 flow. Sequences of >100 consecutive instantaneous velocity images were obtained at a rate of 100 kHz. Velocity fields from both aspects of the hybrid measurement indicated errors less than 1-percent of anticipated velocities. Likewise, all assessments of measurement precision were approximately 1.6-percent of the local velocities. Additional demonstrations in different flowfields including a subsonic axi-symmetric jet and a supersonic Mars reentry vehicle model further illustrate the utility of the new hybrid method.