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Blade tip vortex measurements on actively twisted rotor blades

Bauknecht, André and Ewers, Benjamin and Schneider, Oliver and Raffel, Markus (2017) Blade tip vortex measurements on actively twisted rotor blades. Experiments in Fluids, 58 (49). Springer. DOI: 10.1007/s00348-017-2312-3 ISSN 0723-4864

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Official URL: http:l/link.springer.com/journal/348

Abstract

Active rotor control conce pts, such as active twist actuation, have the pot ential to effectively reduce the noise and vibrations of helicopter roto rs. The present study focuses on the experimental investigation of active twist for the reduction of blade-vortex interaction (BVI) effects on a model rotor. Results of a large-sca le smart-twisting active rotor (STAR) test under hover conditions are described. This test investigated the effects of individual blade twist co ntrol on the blade tip vortices. The rotor blades were actuated with peak torsion amplitudes of up to 2° and harmonic frequencies of 1-5/rev with different phase angles. Time-resolved ste reoscopic pa rt icle image velocimetry (PIV) was ca rried out to study the effect s of active twist on the strength and t rajectories of the t ip vortices between 3.6° and 45.7° of vortex age. The analysis of t he vortex trajectories revea led that t he 1/rev active twist actuation mainly ca used a vertical deflection of the blade t ip and the corresponding vortex trajectories of up to 1.3% of the rotor radius R above and -1%R below the unactuated condit ion. An actuation with frequencies of 2/rev and 3/rev significantly affected the shapes of t he vortex trajectories and caused negative vertical displacements ofthe vortices relative to the unactuat ed case of up to 2%R within the first 35° of wake age. The 2/rev and 3/rev actuation also had the most significant effects on the vortex strength and altered the initial peak swirl velocity by up to -34% and +31% relative to the unactuated value. The present aerodynamic investigation reveals a high control authority of the active twist actuation on the strength and trajectories of the trailing blade tip vortices. The magnitude of the evoked changes indicates that the active twist actuation constitutes an effective measure for the mitigation of BVl-induced noise on helicopters.

Item URL in elib:https://elib.dlr.de/111221/
Document Type:Article
Additional Information:Exp Fluids (2017) 58:49, Published online: 03. April 2017; Volume 58, page number 49
Title:Blade tip vortex measurements on actively twisted rotor blades
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Bauknecht, Andréandre.bauknecht (at) dlr.deUNSPECIFIED
Ewers, Benjaminbenjamin.ewers (at) dlr.deUNSPECIFIED
Schneider, OliverOliver.Schneider (at) dlr.dehttps://orcid.org/0000-0002-0229-0756
Raffel, MarkusMarkus.Raffel (at) dlr.deUNSPECIFIED
Date:2017
Journal or Publication Title:Experiments in Fluids
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:58
DOI :10.1007/s00348-017-2312-3
Publisher:Springer
ISSN:0723-4864
Status:Published
Keywords:rotor hover test, active twist actuation, tip vortex characterization, particle image velocimetry
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
Location: Braunschweig , Göttingen , Stuttgart
Institutes and Institutions:Institute of Technical Physics > Solid State Lasers and Nonlinear Optics
Institute of Flight Systems > Rotorcraft
Institute for Aerodynamics and Flow Technology > Helicopter, GO
Deposited By: Bachmann, Barbara
Deposited On:12 Jun 2017 08:47
Last Modified:06 Sep 2019 15:25

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