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The Tip Vortex System of a Four-Bladed Rotor in Dynamic Stall Conditions

Wolf, C. Christian and Braukmann, Johannes N. and Stauber, Wolfgang and Schwermer, Till and Raffel, Markus (2019) The Tip Vortex System of a Four-Bladed Rotor in Dynamic Stall Conditions. Journal of the American Helicopter Society, 64 (2), pp. 1-14. American Helicopter Society. doi: 10.4050/JAHS.64.022005. ISSN 0002-8711.

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Official URL: https://www.ingentaconnect.com/content/ahs/jahs/pre-prints/content-jahs1996;jsessionid=75rs4ldjn2dgk.x-ic-live-02


The tip vortex system downstream of a four-bladed instrumented rotor was investigated experimentally through the application of stereoscopic particle image velocimetry (PIV). A dynamic stall test case was facilitated by a high cyclic pitch setting of the swashplate, with additional attached-flow and constant-pitch test cases for comparison reasons. The phase-locked PIV system and a rotation of the swashplate assembly allowed for an acquisition of the tip vortex system over the entire dynamic stall cycle and vortex ages up to at least 235°. The vortex structure and its relation to the blade shear layers were studied by means of both phase-averaged flow fields and the identification of vortex properties such as circulation and swirl velocity distributions. When approaching dynamic stall, a breakdown of the vortex structure started at high vortex ages, accompanied by the entrainment of turbulent structures from the passing blade shear layers into the tip vortices. After the flow over the blade is fully separated and during large parts of the downstroke, the wake of the rotor tips appears as a highly turbulent area with no individual tip vortices traceable, before reestablishing an ordered tip vortex structure shortly before the minimum blade pitch angle.

Item URL in elib:https://elib.dlr.de/120331/
Document Type:Article
Title:The Tip Vortex System of a Four-Bladed Rotor in Dynamic Stall Conditions
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Wolf, C. ChristianUNSPECIFIEDhttps://orcid.org/0000-0002-9052-7548UNSPECIFIED
Braukmann, Johannes N.UNSPECIFIEDhttps://orcid.org/0000-0001-8046-9623UNSPECIFIED
Schwermer, TillUNSPECIFIEDhttps://orcid.org/0000-0002-6918-4480UNSPECIFIED
Raffel, MarkusUNSPECIFIEDhttps://orcid.org/0000-0002-3340-9115133716041
Date:8 April 2019
Journal or Publication Title:Journal of the American Helicopter Society
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 1-14
EditorsEmailEditor's ORCID iDORCID Put Code
Publisher:American Helicopter Society
Keywords:blade tip vortex, particle image velocimetry (PIV), rotor test facility
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:24 Apr 2019 09:20
Last Modified:08 Nov 2023 09:43

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