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MHz-rate flow visualization and Planar Doppler Velocimetry (PDV) measurements were carried out in Mach 1.3 and 2.0 axisymmetric jets with Reynolds number based on the nozzle exit diameter of over 10 6 using a burst mode laser and a pair of high-speed CCD framing cameras. Determination of convective velocity from flow visualization using planar space-time correlation reveals strong evidence of bias due to distinct artificial seeding gradients resulting from partial seeding of the flow (i.e. seeding of the mixing region, but not the jet core and the ambient). This bias can be somewhat rectified if the measurements are restricted to the early part of the shear layer growth, where the structures are relatively coherent and the correlation level is high and contains a distinct peak. The bias can be nearly eliminated if the entire flow field is seeded and PDV, rather than flow visualization, is used to determine the convective velocity. Under these circumstances, the measured convective velocity agrees very well with theoretical predictions.

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Temporally resolved PDV is further developed by extending the technique from one component to two components. This is achieved by using a pulse burst laser with MHz rate repetition capabilities and two ultra-high speed framing rate CCD cameras. Each camera is used in a conventional splitter/recombiner PDV system to measure one component of velocity. These two measurements are then combined to resolve the u and w components of velocity. Very preliminary results on a newly constructed planar shear layer facility show the strong potential of this technique and identify a few issues that must be addressed in the next iteration of experiments.