A novel wavefront measuring camera for quantitative measurement of density in high-speed gas flows

Medhi, Biswajit and Hegde, Gopalkrishna M and Reddy, Kalidevapura Polareddy Jagannath and Roy, Debasish and Vasu, Ram Mohan (2018) A novel wavefront measuring camera for quantitative measurement of density in high-speed gas flows. In: REVIEW OF SCIENTIFIC INSTRUMENTS, 89 (8).

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Abstract

This paper presents the development of a novel wavefront measuring camera capable of detecting both the amplitude and phase of the captured light wave simultaneously. The main objective of the present work is to develop a simple ``aim and shoot'' camera system for quantitative estimation of density variations in high-speed gas flow fields. The interrogating beam which is a plane wave used here gets distorted by flow induced change in refractive index gradients. Wavefront distortion is quantitatively measured by inspecting the projected pattern through the embedded mask of a modified CMOS image sensor, which samples the incoming wavefront space continuously. Post-processing of the captured images through Fourier-and wind owed Fourier transform schemes reveals the change in phase and amplitude of the captured wave. The captured phase of the wavefront is used in an iterative tomography scheme to estimate the density distribution of the flow field. The utility of the developed camera is demonstrated in the quantitative visualization of the high-speed flowfields around test objects subjected to hypersonic flows at Mach numbers 8.89 and 5.82 in hypersonic shock tunnel facility (HST2) and also to visualize the flow field generated at the exit of a convergent-divergent nozzle (Mach number 2.9). It is observed that the recovered quantitative density values from the experiments match well with the results obtained through computational fluid dynamic simulations demonstrating the proficiency of the proposed wavefront measuring camera for high-speed flow diagnostics. Published by AIP Publishing.

Item Type:	Journal Article
Publication:	REVIEW OF SCIENTIFIC INSTRUMENTS
Publisher:	AMER INST PHYSICS
Additional Information:	Copy right for this article belong to AMER INST PHYSICS, 1305 WALT WHITMAN RD, STE 300, MELVILLE, NY 11747-4501 USA
Department/Centre:	Division of Mechanical Sciences > Aerospace Engineering(Formerly Aeronautical Engineering) Division of Mechanical Sciences > Civil Engineering Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering Division of Physical & Mathematical Sciences > Instrumentation Appiled Physics
Date Deposited:	27 Sep 2018 14:48
Last Modified:	27 Sep 2018 14:48
URI:	http://eprints.iisc.ac.in/id/eprint/60759

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