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Combining Simultaneous Density and Velocity Measurements of Rotor Blade Tip Vortices under Cyclic Pitch Conditions

Braukmann, Johannes N. and Goerttler, Andreas and Wolf, Christian and Schwarz, Clemens and Raffel, Markus (2021) Combining Simultaneous Density and Velocity Measurements of Rotor Blade Tip Vortices under Cyclic Pitch Conditions. Experiments in Fluids, 62 (9), pp. 1-19. Springer. doi: 10.1007/s00348-021-03281-w. ISSN 0723-4864.

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Official URL: https://doi.org/10.1007/s00348-021-03281-w

Abstract

An investigation into blade tip vortices of a sub-scale rotor under cyclic pitch conditions is carried out. Background oriented schlieren (BOS), particle image velocimetry (PIV), and computational fluid dynamics (CFD) are applied to the same test cases. This approach allows to combine the velocity data from PIV in a measurement plane, the density related data from BOS in a measurement volume, and the comprehensive set of flow variables provided by unsteady detached eddy simulations. Vortices up to an age of Ψv=70∘ in case of PIV and CFD, and up to Ψv=200∘ in case of BOS are considered. The vortex locations are obtained through all three techniques. The unsteadiness of the vortices was obtained by the experimental results, whereas CFD provides an average solution. An increased position scatter was observed during the downstroke of the pitch cycle with both experimental methods and was found to be in good agreement. In the second part, the PIV velocity data are compared to common vortex models. An approach to link the density distribution and the swirl velocity is applied to the measured data. Based on the CFD results, it is shown that the assumption of isothermal flow yields better agreement between velocity and density than isentropic flow.

Item URL in elib:https://elib.dlr.de/144608/
Document Type:Article
Title:Combining Simultaneous Density and Velocity Measurements of Rotor Blade Tip Vortices under Cyclic Pitch Conditions
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Braukmann, Johannes N.Johannes.Braukmann (at) dlr.dehttps://orcid.org/0000-0001-8046-9623
Goerttler, AndreasAndreas.Goerttler (at) dlr.deUNSPECIFIED
Wolf, ChristianChristian.Wolf (at) dlr.dehttps://orcid.org/0000-0002-9052-7548
Schwarz, ClemensClemens.Schwarz (at) dlr.deUNSPECIFIED
Raffel, MarkusMarkus.Raffel (at) dlr.dehttps://orcid.org/0000-0002-3340-9115
Date:6 September 2021
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
Open Access:Yes
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:62
DOI :10.1007/s00348-021-03281-w
Page Range:pp. 1-19
Editors:
EditorsEmailEditor's ORCID iD
UNSPECIFIEDSpringerUNSPECIFIED
Publisher:Springer
ISSN:0723-4864
Status:Published
Keywords:Blade tip vortices, PIV, BOS, experiments
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:03 Nov 2021 11:24
Last Modified:03 Nov 2021 11:24

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