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Development of secondary vortex structures in rotor wakes

Schwarz, Clemens and Bodling, Andrew and Wolf, Christian and Brinkema, Robert and Potsdam, Mark and Gardner, Anthony (2022) Development of secondary vortex structures in rotor wakes. Experiments in Fluids, 63 (4), pp. 1-21. Springer Nature. doi: 10.1007/s00348-021-03348-8. ISSN 0723-4864.

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Official URL: https://link.springer.com/article/10.1007/s00348-021-03348-8


The blade tip vortex system is a crucial feature in the wake of helicopter rotors, and its correct prediction represents a major challenge in the numerical simulation of rotor flows. A common phenomenon in modern high-fidelity CFD simulations is the breakdown of the primary vortex system in hover due to secondary vortex braids. Since they are strongly influenced by the numerical settings, the degree to which these secondary vortex structures actually physically occur is still discussed and needs experimental validation. In the current work, the development of secondary vortex structures in the wake of a two-bladed rotor in hover conditions was investigated by combining stereoscopic particle image velocimetry measurements in different measurement planes and high-fidelity simulations. Secondary vortex structures were detected and quantified at different axial locations in the wake by applying an identical scheme to the measured and simulated velocity data. In agreement, it was found that the number of secondary vortices is maximum at a distance of 0.8R below the rotor. The more intense secondary vortex structures were quantitatively well captured in the simulation, whereas in the experiment a larger number of weaker vortices were detected. No distinct preferential direction of rotation was found for the secondary vortices, but they tended to develop in vortex pairs with alternating sense of rotation. A clustered occurrence of secondary vortices was observed close to the primary tip vortices, where the rolled-up blade shear layer breaks down into coherent vortex structures.

Item URL in elib:https://elib.dlr.de/191161/
Document Type:Article
Additional Information:Published Online: December 2021 Citation: print version 2022
Title:Development of secondary vortex structures in rotor wakes
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Bodling, AndrewScience and Technology CorporationUNSPECIFIEDUNSPECIFIED
Wolf, ChristianUNSPECIFIEDhttps://orcid.org/0000-0002-9052-7548UNSPECIFIED
Potsdam, MarkU.S. Army Combat Capabilities Development Command Aviation & Missile CenterUNSPECIFIEDUNSPECIFIED
Gardner, AnthonyUNSPECIFIEDhttps://orcid.org/0000-0002-1176-3447134929528
Date:January 2022
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 1-21
EditorsEmailEditor's ORCID iDORCID Put Code
Publisher:Springer Nature
Keywords:rotor wake, secondary vortices, PIV, CFD
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Aeronautics
HGF - Program Themes:Efficient Vehicle
DLR - Research area:Aeronautics
DLR - Program:L EV - Efficient Vehicle
DLR - Research theme (Project):L - Virtual Rotorcraft and Validation
Location: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, GO
Deposited By: Carter, Beatrice
Deposited On:06 Dec 2022 11:26
Last Modified:27 Jun 2023 15:05

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