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Proceedings Paper

Quantification of frozen flow properties for a turbulent mixing layer of helium and nitrogen gas
Author(s): Patrick J. Gardner; Michael C. Roggemann; Byron M. Welsh
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Paper Abstract

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.

Paper Details

Date Published: 14 October 1996
PDF: 10 pages
Proc. SPIE 2828, Image Propagation through the Atmosphere, (14 October 1996); doi: 10.1117/12.254174
Show Author Affiliations
Patrick J. Gardner, Air Force Institute of Technology (United States)
Michael C. Roggemann, Air Force Institute of Technology (United States)
Byron M. Welsh, Air Force Institute of Technology (United States)

Published in SPIE Proceedings Vol. 2828:
Image Propagation through the Atmosphere
Christopher Dainty; Luc R. Bissonnette, Editor(s)

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