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Extension of Doppler global velocimetry to periodic flows

A three-component, time- and phase-averaging Doppler global velocimetry (DGV) system was developed. Measurements were performed in the cold exhaust flow of a piston engine at two different rotational speeds, with an angular resolution of 5° with respect to the cam-shaft angle. The results gave a very detailed insight into the temporal evolution of the flow field. Phase-averaged DGV measurements were performed in the unsteady periodic flow of a generic swirl nozzle using an acoustic trigger. The measurements help to identify the phenomena of a precessing vortex core. The measurement accuracy of the DGV system was investigated.