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A method for optical measurements of film height distributions in transparent media

Lenk, Sebastian and Westhoff, Andreas and Wagner, Claus (2013) A method for optical measurements of film height distributions in transparent media. In: New Results in Numerical and Experimental Fluid Mechanics VIII Notes on Numerical Fluid Mechanics and Multidisciplinary Design, 121. Springer Verlag, Heidelberg New York Dordrecht London. pp. 673-680. ISBN 978-3-642-35679-7. ISSN 1612-2909

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Official URL: http://link.springer.com/chapter/10.1007%2F978-3-642-35680-3_80

Abstract

As light passes the interface between two media with different densities, the light will be refracted which leads to an optical beam displacement. In this paper we present a simple optical and non-invasive measurement technique and a reconstructing algorithm needed to determine the height distribution of a transparent medium. The local height of one medium is reconstructed using Snell’s law after measuring the beam displacement. Thereto, the optical displacement on a two dimensional background plane is obtained by using background oriented schlieren and spatial cross-correlation with reference imaging. Moreover, to rebuilt the three dimensional height distribution from the image plane, a camera calibration is required. As long as the interface between the two media is plan-parallel to the background plane, the presented method provides a unique solution with only one camera. In this paper we show that this simple reconstruction algorithm can also be used for reconstructing weakly curved interfaces as well. We also present results of measurement of water droplets on a planar surface, using this algorithm. Furthermore, we discuss the errors, which result from the non plan-parallelity of the interface and show that for strongly curved interfaces the method must be advanced by using spatial displacement gradients or multiple cameras, which allows to reconstruct curvy interfaces more accurately.

Item URL in elib:https://elib.dlr.de/81563/
Document Type:Contribution to a Collection
Additional Information:Online ISBN: 978-3-642-35680-3
Title:A method for optical measurements of film height distributions in transparent media
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Lenk, SebastianSebastian.Lenk (at) dlr.deUNSPECIFIED
Westhoff, AndreasAndreas.Westhoff (at) dlr.deUNSPECIFIED
Wagner, ClausClaus.Wagner (at) dlr.deUNSPECIFIED
Date:2013
Journal or Publication Title:New Results in Numerical and Experimental Fluid Mechanics VIII
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:No
In ISI Web of Science:No
Volume:121
DOI :10.1007/978-3-642-35680-3_80
Page Range:pp. 673-680
Editors:
EditorsEmail
Dillmann, AndreasDLR
Heller, GerdAirbus Deutschland, Bremen, Germany
Kreplin, Hans-PeterDLR
Nitsche , WolfgangTU Berlin, Berlin, Germany
Peltzer, InkenBeechcraft Berlin aviation GmbH, Schönefeld, Germany
Publisher:Springer Verlag, Heidelberg New York Dordrecht London
Series Name:Notes on Numerical Fluid Mechanics and Multidisciplinary Design
ISSN:1612-2909
ISBN:978-3-642-35679-7
Status:Published
Keywords:optical measurement method, film height distributions, transparent media, light refraction, Snell, correlation
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Transport
HGF - Program Themes:Terrestrial Vehicles (old)
DLR - Research area:Transport
DLR - Program:V BF - Bodengebundene Fahrzeuge
DLR - Research theme (Project):V - Projekt Next Generation Train (old)
Location: Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Fluid Systems
Deposited By: Lenk, Sebastian
Deposited On:30 Apr 2013 14:00
Last Modified:02 Mar 2015 15:26

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