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Unsteady Boundary-Layer Transition Measurements and Computations on a Rotating Blade under Cyclic Pitch Conditions

Weiss, Armin and Wolf, C. Christian and Kaufmann, Kurt and Braukmann, Johannes N. and Heineck, James T. and Raffel, Markus (2020) Unsteady Boundary-Layer Transition Measurements and Computations on a Rotating Blade under Cyclic Pitch Conditions. Experiments in Fluids, 61 (61), pp. 1-16. Springer. DOI: 10.1007/s00348-020-2899-7 ISSN 0723-4864

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Official URL: https://link.springer.com/article/10.1007/s00348-020-2899-7

Abstract

The presented work tackles the lack of experimental investigations of unsteady laminar-turbulent boundary-layer transition on rotor blades at cyclic pitch actuation, which are important for accurate performance predictions of helicopters in forward flight. Unsteady transition positions were measured on the blade suction side of a four-bladed subscale rotor by means of non-intrusive differential infrared thermography (DIT). Experiments were conducted at different rotation rates corresponding to Mach and Reynolds numbers at 75% rotor radius of up to M_75=0.21 and Re_75 =3.3×10^5 and with varying cyclic blade pitch settings. The setup allowed transition to be measured across the outer 54% of the rotor radius. For comparison, transition was also measured using conventional infrared thermography for steady cases with collective pitch settings only. The study is complemented by numerical simulations including boundary-layer transition modeling based on semi-empirical criteria. DIT results reveal the upstream and downstream motion of boundary-layer transition during upstroke and downstroke, a reasonable comparison to experimental results obtained using the already established sigma*c_p method, and noticeable agreement with numerical simulations. The result is the first systematic study of unsteady boundary-layer transition on a rotor suction side by means of DIT including a comparison to numerical computations.

Item URL in elib:https://elib.dlr.de/128642/
Document Type:Article
Title:Unsteady Boundary-Layer Transition Measurements and Computations on a Rotating Blade under Cyclic Pitch Conditions
Authors:
AuthorsInstitution or Email of AuthorsAuthor's ORCID iD
Weiss, Arminarmin.weiss (at) dlr.dehttps://orcid.org/0000-0002-7532-2974
Wolf, C. ChristianChristian.Wolf (at) dlr.dehttps://orcid.org/0000-0002-9052-7548
Kaufmann, KurtKurt.Kaufmann (at) dlr.dehttps://orcid.org/0000-0003-2276-3386
Braukmann, Johannes N.Johannes.Braukmann (at) dlr.dehttps://orcid.org/0000-0001-8046-9623
Heineck, James T.NASA Ames Research Center, Moffett Field, CA, USAUNSPECIFIED
Raffel, MarkusMarkus.Raffel (at) dlr.dehttps://orcid.org/0000-0002-3340-9115
Date:12 February 2020
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:61
DOI :10.1007/s00348-020-2899-7
Page Range:pp. 1-16
Editors:
EditorsEmailEditor's ORCID iD
UNSPECIFIEDSpringer NatureUNSPECIFIED
Publisher:Springer
ISSN:0723-4864
Status:Published
Keywords:unsteady boundary-layer transition, rotor blades, differential infrared-thermography (DIT), semi-empirical transition modeling, e^N–method
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
Institute for Aerodynamics and Flow Technology > Experimental Methods, GO
Deposited By: Winkels, Elisabeth
Deposited On:19 Feb 2020 11:52
Last Modified:19 Feb 2020 11:52

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