23 December 2014 Quantitative estimation of density variation in high-speed flows through inversion of the measured wavefront distortion
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Abstract
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.
© 2014 Society of Photo-Optical Instrumentation Engineers (SPIE)
Biswajit Medhi, Gopalkrishna M. Hegde, Kalidevapura Polareddy Jagannath Reddy, Debasish Roy, Ram Mohan Vasu, "Quantitative estimation of density variation in high-speed flows through inversion of the measured wavefront distortion," Optical Engineering 53(12), 124107 (23 December 2014). https://doi.org/10.1117/1.OE.53.12.124107 . Submission:
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