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29 December 1992 Experimental investigation of simultaneously recorded shadowgraphs and images through a high-velocity turbulent flow
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Abstract
Experiments were conducted by Teledyne Brown Engineering (TBE), that simultaneously recorded flow field shadowgraphs and imaging data, to investigate the relationship between high velocity turbulence and aero-optic image distortion. A laboratory based Dual Nozzle Aero-Optic Simulator (DNAOS) was used to produce a turbulent flight level aero-optic environment similar to that encountered by a hypersonic vehicle. An Nd:YAG laser, operating at 1.064 micrometers , was expanded to 5 mm, collimated, and directed through the turbulent flow field to serve as a point source at infinity. On the opposite side of the flow field, the beam was split into two components and directed towards two 60 micrometers square pixelated, 128 X 128 CCD array cameras. One camera had a bare focal plane and was used to record the turbulence induced scattering field (shadowgraph), while the other had a 3.4 m focal length lens to image this field, producing a point-spread-function (PSF) on the CCD array. A 50 nsec duration laser pulse at a frequency of 92.5 Hz (frame rate of the CCD cameras) was recorded by each of the cameras and the data was digitized by a high speed data acquisition system. The shadowgraphs and imaging data were compared frame-for-frame to determine the similarities between the flow field events and the image distortion. Based on this analysis, a procedure has been proposed to numerically transform shadowgraphs to obtain pseudo-images that could be compared to experimentally recorded images.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Jeffrey S. Haight, Bruce R. Peters, David A. Kalin, Lori C. Brooks, and Jason M. Kinser "Experimental investigation of simultaneously recorded shadowgraphs and images through a high-velocity turbulent flow", Proc. SPIE 1767, Inverse Problems in Scattering and Imaging, (29 December 1992); https://doi.org/10.1117/12.139029
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