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Quantitative estimation of density variation in high-speed flows through inversion of the measured wavefront distortion

Medhi, Biswajit and Hegde, Gopalkrishna Mahadeva and Reddy, Kalidevapura Polareddy Jagannath and Roy, Debasish and Vasu, Ram Mohan (2014) Quantitative estimation of density variation in high-speed flows through inversion of the measured wavefront distortion. In: OPTICAL ENGINEERING, 53 (12).

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Official URL: http://dx.doi.org/ 10.1117/1.OE.53.12.124107


A simple method employing an optical probe is presented to measure density variations in a hypersonic flow obstructed by a test model in a typical shock tunnel. The probe has a plane light wave trans-illuminating the flow and casting a shadow of a random dot pattern. Local slopes of the distorted wavefront are obtained from shifts of the dots in the pattern. Local shifts in the dots are accurately measured by cross-correlating local shifted shadows with the corresponding unshifted originals. The measured slopes are suitably unwrapped by using a discrete cosine transform based phase unwrapping procedure and also through iterative procedures. The unwrapped phase information is used in an iterative scheme for a full quantitative recovery of density distribution in the shock around the model through refraction tomographic inversion. Hypersonic flow field parameters around a missile shaped body at a free-stream Mach number of 5.8 measured using this technique are compared with the numerically estimated values. (C) 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)

Item Type: Journal Article
Additional Information: Copy right for this article belongs to the SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 1000 20TH ST, PO BOX 10, BELLINGHAM, WA 98225 USA
Keywords: wavefront sensors; flows; tomography; image reconstruction; sensors; shock
Department/Centre: Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering)
Division of Mechanical Sciences > Civil Engineering
Division of Physical & Mathematical Sciences > Instrumentation Appiled Physics
Date Deposited: 04 Mar 2015 12:23
Last Modified: 04 Mar 2015 12:23
URI: http://eprints.iisc.ac.in/id/eprint/50966

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