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A Novel Experiment to Understand the Dynamic Stall Phenomenon in Rotor Axial Flight

Schwermer, Till and Gardner, Anthony D. and Raffel, Markus (2019) A Novel Experiment to Understand the Dynamic Stall Phenomenon in Rotor Axial Flight. Journal of the American Helicopter Society, 64 (1), pp. 1-11. American Helicopter Society. DOI: 10.4050/JAHS.64.012004 ISSN 0002-8711

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Official URL: https://doi.org/10.4050/JAHS.64.012004

Abstract

A rotor test facility was developed to investigate dynamic stall under optimized boundary conditions compared to conventional hover chambers. lt features a defined axial inflow, reduction of ground effect and recirculation of the rotor wake and good optical access to apply non-intrusive measuring techniques. The rotor consists of two blades with an aspect ratio of 6.8 and a tip radius of 0.65m. lt was operated at a Mach number of 0.21 and a chord based Reynolds number of 350000, both at 75% radius. The flow and blade deformation were analyzed by means of unsteady blade pressure transducers, particle image velocimetry and tip deflection measurements covering the whole azimuth and different radii. Three measurement approaches to detect flow separation: tufts, differential infrared thermography and surface pressure analysis showed comparable results and flow separation over one half of the cycle. A radiusdependent separation point in time and an altering of the dynamic stall behavior near the tip were observed. The recirculation area remained close to the blade's surface with radial jet flow increasing towards the tip. A maximum increase of the effective angle of attack of 1.4° was observed due to blade deformation. For a fully attached flow case the laminar-turbulent boundary layer transition differed along the radius and moved over 70% of the blade's chord.

Item URL in elib:https://elib.dlr.de/111646/
Document Type:Article
Title:A Novel Experiment to Understand the Dynamic Stall Phenomenon in Rotor Axial Flight
Authors:
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Schwermer, TillTill.Schwermer (at) alumni-uni-hannover.dehttps://orcid.org/0000-0002-6918-4480
Gardner, Anthony D.anthony.gardner (at) dlr.dehttps://orcid.org/0000-0002-1176-3447
Raffel, MarkusMarkus.Raffel (at) dlr.dehttps://orcid.org/0000-0002-3340-9115
Date:1 January 2019
Journal or Publication Title:Journal of the American Helicopter Society
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In SCOPUS:Yes
In ISI Web of Science:Yes
Volume:64
DOI :10.4050/JAHS.64.012004
Page Range:pp. 1-11
Editors:
EditorsEmail
UNSPECIFIEDAHS - Vertical Flight Society
Publisher:American Helicopter Society
ISSN:0002-8711
Status:Published
Keywords:Dynamic Stall, Rotor, Aerodynamics, PIV, RTG, Rotor Test Facility, Helicopter, Hover Chamber
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: Göttingen
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, GO
Deposited By: Winkels, Elisabeth
Deposited On:20 Dec 2017 15:29
Last Modified:05 Jun 2019 17:20

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