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Airborne visualization of helicopter blade tip vortices

Bauknecht, Andre and Merz, Christoph B. and Raffel, Markus (2016) Airborne visualization of helicopter blade tip vortices. Journal of Visualization, 20, pp. 139-150. Springer. doi: 10.1007/s12650-016-0389-z. ISSN 1343-8875.

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Official URL: https://doi.org/10.1007/s12650-016-0389-z


Blade tip vortices and their interaction with the helicopter blades play an important role in the generation of noise on rotorcraft. Full-scale vortex visualization is essential for the understanding of these effects and the validation of sub-scale experiments and numerical simulations. In the present work, the reference-free background-oriented schlieren (BOS) method was used to visualize blade tip vortices of a full-scale BO 105 helicopter in hover and under free-flight conditions. A ground-based dual camera BOS system with an artificial background was applied for the visualization of the helicopter's main and tail rotor tip vortices during take-off. In a second flight test, a similar dual-camera BOS system was used to visualize the main rotor blade tip vortices of the BO 105 during high-speed forward, curve, and accelerating forward flight. The camera system was deployed aboard a microlight airplane flying above the helicopter, with vegetation on the ground serving as natural backgrounds. Different natural and artificial backgrounds were analyzed and compared to assess their suitability for the BOS evaluation. The airborne setup enabled the visualization of vortices up to a maximum vortex age of 630 deg at distances of up to one rotor diameter behind the rotor plane. Blade-vortex interaction effects and deformations of the vortex system were observed. The visualization results obtained during the inflight measurements show that the reference-free BOS method is highly suitable for the detection of helicopter blade tip vortices during full-speed forward and maneuvering flight, therefore removing the restrictions imposed by ground-based measurements.

Item URL in elib:https://elib.dlr.de/105750/
Document Type:Article
Additional Information:First Online: 02 September 2016
Title:Airborne visualization of helicopter blade tip vortices
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Bauknecht, Andreandre.bauknecht (at) dlr.deUNSPECIFIED
Merz, Christoph B.christoph.merz (at) dlr.deUNSPECIFIED
Raffel, Markusmarkus.raffel (at) dlr.deUNSPECIFIED
Date:2 September 2016
Journal or Publication Title:Journal of Visualization
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
DOI :10.1007/s12650-016-0389-z
Page Range:pp. 139-150
EditorsEmailEditor's ORCID iD
Keywords:background-oriented schlieren, helicopter, flight test, blade tip vortex, visualization
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 of Aerodynamics and Flow Technology > Helicopters
Deposited By: Bachmann, Barbara
Deposited On:11 Jan 2017 14:16
Last Modified:04 Nov 2020 23:10

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