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Focused laser differential interferometer response to shock waves

Lawson, J. M. and Austin, J. M. (2021) Focused laser differential interferometer response to shock waves. Measurement Science and Technology, 32 (5). Art. No. 055203. ISSN 0957-0233. doi:10.1088/1361-6501/abdbd3.

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The focused laser differential interferometer (FLDI) can be used to measure rapid density fluctuations non-intrusively in high-speed flow applications. Being a non-imaging shearing interferometer, FLDI response can be accurately modeled using a paraxial ray-tracing scheme. We present the details of a new numerical implementation of this scheme, capable of accepting flow-field input from analytical models, computational fluid dynamics (CFD) results, and experimental data. This implementation has previously been validated for static (laminar jet) and dynamic (ultrasound-generated) changes in index of refraction by Lawson et al. In this work, we examine the FLDI response to shock waves propagating at up to Mach 10, in Caltech's hypervelocity expansion tube. While the timescale and approximate form of the signal can be recovered using a simple inviscid, planar shock model, it is found that the inclusion of viscous shock effects allows an accurate simulation of both the magnitude and detailed shape of the experimental response. This is a further analytical validation of the FLDI model that extends beyond the results of the existing dynamic validation case. The model implementation is then coupled to a CFD code, and predictions reproduce experimental FLDI response to a complex shock-dominated flow-field.

Item Type:Article
Related URLs:
URLURL TypeDescription
Lawson, J. M.0000-0002-3042-0909
Austin, J. M.0000-0003-3129-5035
Additional Information:© 2021 IOP Publishing Ltd. Received 12 November 2020, revised 16 December 2020; Accepted for publication 14 January 2021; Published 12 March 2021. The authors gratefully acknowledge Prof J E Shepherd of Caltech for his ongoing interest in furthering our understanding and application of FLDI. They would also like to thank Prof R Deiterding of the University of Southampton for his patient assistance with the operation of AMROC. This work was partially supported by the Office of Naval Research award N00014-16-1-2503 with Dr Eric Marineau.
Funding AgencyGrant Number
Office of Naval Research (ONR)N00014-16-1-2503
Subject Keywords:interferometry, hypersonics, FLDI
Issue or Number:5
Record Number:CaltechAUTHORS:20210318-123606611
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Official Citation:J M Lawson and J M Austin 2021 Meas. Sci. Technol. 32 055203
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:108486
Deposited By: Tony Diaz
Deposited On:19 Mar 2021 00:12
Last Modified:12 Jul 2022 19:44

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