Time Resolved Doppler Global Velocimetry

Time-Resolved Doppler Global Velocimetry (TRDGV) is a novel approach for obtaining a grid of velocity vectors at very high sampling rates. As with Doppler Global Velocimetry/Planar Doppler Velocimetry(DGV/PDV), TRDGV relies on the detection of the Doppler shift of laser light scattered by particles (Mie scattering) following the local flow. By carefully tuning the frequency of a single-longitudinal-mode laser to a transition in the optical absorption characteristics of an iodine vapor filter, the frequency of the scattered light is effectively transduced to intensity of light passing through the iodine filter.

We apply TRDGV in supersonic jet flows for the study of flow physics related to jet noise. The approach discussed in the references listed below has been demonstrated to flow acquistion rates of 250 kHz, while higher acquisition rates are within the capabilities of our hardware. The approach is scalable and has been applied in our laboratory jet at Virginia Tech, the moderate scale Nozzle Acoustics Test Rig at NASA Glenn Research Center, and at the JT15D-1a research turbofan engine at Virginia Tech. Further measurements are planned in full-scale, modern tactical exhaust plumes.

Relevant publications:

1. Ecker T*, Lowe K T and Ng W F 2015 “A rapid response 64-channel photomultiplier tube camera for high-speed flow velocimetry,” Measurement Science and Technology, 26(2), 027001, 6pp.
2. Ecker T,* Brooks DR* , Lowe KT and Ng W 2014 “Development and application of a point Doppler velocimeter featuring two-beam multiplexing for time-resolved measurements of high speed flow,” Experiments in Fluids, 55, 1819-1833.
3. Ecker TE*, Lowe KT and Ng WF 2016 “Development of Doppler global velocimetry for the measurement of eddy convective velocities,” 18th Intl. Symposium Appl. Laser Techniques and Imaging to Fluid Mech., Lisbon, Portugal, 4-7 July, paper 2.2.3.
4. Ecker T*, Lowe KT, and Ng W 2016 “Scale-up of the time-resolved Doppler global velocimetry technique,” AIAA SciTech 2016, San Diego, CA, 4-8 January, paper AIAA-2016-0029.