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Influence of a back-flow flap on the dynamic stall flow topology

Wolf, Christian C. and Gardner, Anthony and Merz, Christoph B. and Opitz, Steffen (2018) Influence of a back-flow flap on the dynamic stall flow topology. CEAS Aeronautical Journal, 9 (39), pp. 39-51. Springer. doi: 10.1007/s13272-017-0274-z. ISSN 1869-5590.

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Official URL: https://link.springer.com/article/10.1007/s13272-017-0274-z


Dynamic stall is a major concern for highly loaded helicopter rotors in fast forward flight. The potential of a backflow flap for dynamic stall reduction is investigated. The flap assembly is mounted on the suction side of a helicopter airfoil undergoing deep-stall pitch oscillations. Wind-tu nnel experiments using high-speed particle image velocimetry were conducted to identify the flow topology and to imiestigate the flap's method of operation. A phaseaveraged proper orthogonal decomposition (POD) is used to identify relevant flow events and to compare test cases with and without flap. The evolution of the la rge-scale dynamic stall vortex in the in itial phases of flow separation is analyzed in detail. The back-flow flap splits the vortex into two smaller vortices and thereby reduces the pitching moment peak. This effect can be described through the eigenmode coefficients of the POD. The study closes with an analysis of different pitching frequencies, which do not affect the flap's method of operation.

Item URL in elib:https://elib.dlr.de/111117/
Document Type:Article
Additional Information:First online: 13. November 2017; Online ISSN: 1869-5590; Druckversion erschienen: März 2018; Print ISSN: 1869-5582
Title:Influence of a back-flow flap on the dynamic stall flow topology
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Wolf, Christian C.UNSPECIFIEDhttps://orcid.org/0000-0002-9052-7548UNSPECIFIED
Gardner, AnthonyUNSPECIFIEDhttps://orcid.org/0000-0002-1176-3447137131920
Opitz, SteffenUNSPECIFIEDhttps://orcid.org/0000-0003-1257-547X137131923
Journal or Publication Title:CEAS Aeronautical Journal
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:No
Page Range:pp. 39-51
Series Name:Springer Nature
Keywords:Helicopter rotor, Wind tunnel, Flow control, Dynamic stall, Experiment
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: Braunschweig , Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, GO
Institute of Composite Structures and Adaptive Systems > Multifunctional Materials
Deposited By: Bachmann, Barbara
Deposited On:17 Nov 2017 11:04
Last Modified:21 Nov 2023 14:29

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