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Reference-free Digital Shadowgraphy Using a Moving BOS Background

Gardner, Anthony D. and Raffel, Markus and Schwarz, Clemens and Braukmann, Johannes N. and Wolf, C. Christian (2020) Reference-free Digital Shadowgraphy Using a Moving BOS Background. Experiments in Fluids, 61 (44), pp. 1-5. Springer Nature. doi: 10.1007/s00348-019-2865-4. ISSN 0723-4864.

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Official URL: https://link.springer.com/article/10.1007/s00348-019-2865-4


A method of measuring density second derivative (shadowgraph) as a variant of background oriented schlieren (BOS) is presented. Pairs of images of a moving background with a small time difference are analysed using moving-window crosscorrelation, giving the second derivative of density in the axis of background travel. The advantage over standard BOS is that no reference image is required. In contrast to the existing "reference-free BOS" method, no double-image is produced, making the data interpretation simpler. The sum-of-correlation (ensemble correlation) method can be used on an image series, where the flow is constant over the series time, to significantly reduce the size of the cross-correlation window. The reduction in the window size and sharpening of the resulting image is similar to that achieved by optical flow, but this method is easily automatable, without knowledge of the flow, and can be used with any existing BOS analysis software.

Item URL in elib:https://elib.dlr.de/133838/
Document Type:Article
Title:Reference-free Digital Shadowgraphy Using a Moving BOS Background
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Gardner, Anthony D.UNSPECIFIEDhttps://orcid.org/0000-0002-1176-3447134929516
Raffel, MarkusUNSPECIFIEDhttps://orcid.org/0000-0002-3340-9115133716092
Braukmann, Johannes N.UNSPECIFIEDhttps://orcid.org/0000-0001-8046-9623UNSPECIFIED
Wolf, C. ChristianUNSPECIFIEDhttps://orcid.org/0000-0002-9052-7548UNSPECIFIED
Date:21 January 2020
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 1-5
EditorsEmailEditor's ORCID iDORCID Put Code
Publisher:Springer Nature
Keywords:BOS, shadowgraphy, density gradient, measurement techniques, optical measurement
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:rotorcraft
DLR - Research area:Aeronautics
DLR - Program:L RR - Rotorcraft Research
DLR - Research theme (Project):L - The Virtual Aerodynamic Rotorcraft (old)
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, GO
Deposited By: Winkels, Elisabeth
Deposited On:19 Feb 2020 13:30
Last Modified:23 Oct 2023 12:35

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