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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. 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

Abstract

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
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Gardner, Anthony D.anthony.gardner (at) dlr.dehttps://orcid.org/0000-0002-1176-3447
Raffel, MarkusMarkus.Raffel (at) dlr.dehttps://orcid.org/0000-0002-3340-9115
Schwarz, ClemensClemens.Schwarz (at) dlr.deUNSPECIFIED
Braukmann, Johannes N.Johannes.Braukmann (at) dlr.dehttps://orcid.org/0000-0001-8046-9623
Wolf, C. ChristianChristian.Wolf (at) dlr.dehttps://orcid.org/0000-0002-9052-7548
Date:21 January 2020
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:61
DOI :10.1007/s00348-019-2865-4
Page Range:pp. 1-5
Editors:
EditorsEmailEditor's ORCID iD
UNSPECIFIEDSpringerUNSPECIFIED
Publisher:Springer
ISSN:0723-4864
Status:Published
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
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:19 Feb 2020 13:30

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