14 October 1996 Quantification of frozen flow properties for a turbulent mixing layer of helium and nitrogen gas
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Two high-speed cameras were used to generate a set of measurements of laser light propagating through a high- Reynolds-number mixing layer. A channel-flow mix of helium gas at 4.5 m/s and nitrogen gas at 1.0 m/s induced optical perturbations which were sensed using shadowgraph and wave front slope measurements. Phase surfaces were reconstructed from the wave front slopes. An ensemble of 255 frame- registered measurements were obtained for each sensing technique at eight aperture locations in the flow, spaced between 0 cm and 15 cm from the exit nozzle of the turbulence generator. A technique is introduced which computes an array of correlation coefficients over a two- dimensional sliding window for various temporal separations as a means to quantify frozen flow properties. For the wave front phase, the peaks of the correlation coefficient arrays degraded by 30 to 60 percent for 1 ms separation, indicative of limited validity in a frozen flow assumption for this type of flow.
© (1996) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Patrick J. Gardner, Michael C. Roggemann, Byron M. Welsh, "Quantification of frozen flow properties for a turbulent mixing layer of helium and nitrogen gas", Proc. SPIE 2828, Image Propagation through the Atmosphere, (14 October 1996); doi: 10.1117/12.254174; https://doi.org/10.1117/12.254174

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