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Visualization of vortical structures by density gradient detection

Richard, H. and Raffel, M. (2001) Visualization of vortical structures by density gradient detection. In: The 3rd Pacific Symposium on Flow Visualization and Image Processing, 14Seiten-. PSFVIP-3, Maui, Hawaii, USA, 18.-21.03.2001. ISBN 1-930746-01-6.

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Abstract

Applications of an advanced schlieren technique, in the following referred to as Backround Oriented Schlieren (BOS) (Richard et al, 2000) or synthetic schlieren (Dalziel et al, 2000), are presented. Three experimental studies have been carried out in order to investigate compressible vortices. Beside other things, those vortices play a major role in the blade vortex interaction (BVI) phenomena, which leads to the typical impulsive noise at helicopters. Therefore, two experiments have been performed in order to investigate details of vortex formation from blade tips of two different helicopters in flight: an Eurocopter BK117 and a large US utility helicopter. Simultaneous measurements of the velocity and density fields have then been conducted to characterize the struture of compressible vortices. The background oriented technique appears to well complement other optical techniques like shadowgraphy or focussing schlieren methods and yield additional quantitative information. Furthermore, in the case of helicopter aerodynamics, this technique allows the effect of Reynolds number on vortex development from blade tips to be studied in full-scale flight tests more easily than using laser-based techniques.

Document Type:Conference or Workshop Item (Paper)
Additional Information: LIDO-Berichtsjahr=2001, monograph_id=Conference-Paper No. F3013,
Title:Visualization of vortical structures by density gradient detection
Authors:
AuthorsInstitution or Email of Authors
Richard, H.UNSPECIFIED
Raffel, M.UNSPECIFIED
Date:2001
Journal or Publication Title:The 3rd Pacific Symposium on Flow Visualization and Image Processing
Page Range:14Seiten-
Editors:
EditorsEmail
Prof. T. Kobayashi, UNSPECIFIED
Series Name:CD-ROM Proceedings
ISBN:1-930746-01-6
Status:Published
Keywords:density, visualization, background, schlieren, full-scale, vortex
Event Title:PSFVIP-3, Maui, Hawaii, USA, 18.-21.03.2001
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Aeronautics
HGF - Program Themes:other
DLR - Research area:Aeronautics
DLR - Program:L ST - Starrflüglertechnologien
DLR - Research theme (Project):UNSPECIFIED
Location: Köln-Porz , Braunschweig , Göttingen
Institutes and Institutions:Institute of Aerodynamics and Flow Technology > Institut für Strömungsmechanik
Deposited By: Ilka Micknaus
Deposited On:16 Sep 2005
Last Modified:14 Jan 2010 20:58

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