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A Method for Approximate Prediction of Laminar-Turbulent Transition on Helicopter Rotors

Heister, C. C. (2018) A Method for Approximate Prediction of Laminar-Turbulent Transition on Helicopter Rotors. Journal of the American Helicopter Society, 63 (3), pp. 1-14. American Helicopter Society. doi: 10.4050/JAHS.63.032008. ISSN 0002-8711.

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An approximate method is presented to predict the laminar-turbulent transition onset within the unsteady Reynolds-averaged Navier-Stokes (URANS) simulations of helicopter rotors. Based on the presented method, the influence of laminar flow on the required rotor power and generated rotor thrust is investigated and compared to fully turbulent results. To compute the laminar boundary layer, an integral method according to Schlichting/Walz and a set of rotating velocity profiles according to Blaser and Velkoff are used. The laminar-turbulent transition onset is predicted by empirical criteria with respect to Tollmien-Schlichting and crossflow instabilities, bypass mechanisms, and attachment line contamination. The method presented accounts for the turbulence-level variation of the simulated rotor wake. A detection of the boundary layer edge within the URANS solution is not required. The approximate method is validated using the experimental onset positions of representative transition test cases. This includes a laminar flow airfoil and a swept wing. To cover a rotor in forward flight, the onset positions on the model rotor of a Mach-scaled helicopter configuration are computed and compared to available hot-film measurements. In general, the predicted laminar flow lengths on the rotor blades reduce the required rotor power by 4-5%. The rotor thrust remains practically unaffected.

Item URL in elib:https://elib.dlr.de/120769/
Document Type:Article
Title:A Method for Approximate Prediction of Laminar-Turbulent Transition on Helicopter Rotors
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Date:3 July 2018
Journal or Publication Title:Journal of the American Helicopter Society
Refereed publication:Yes
Open Access:No
Gold Open Access:No
In ISI Web of Science:Yes
Page Range:pp. 1-14
EditorsEmailEditor's ORCID iDORCID Put Code
Publisher:American Helicopter Society
Keywords:helicopter, aerodynamics, transition
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: Braunschweig
Institutes and Institutions:Institute for Aerodynamics and Flow Technology > Helicopter, BS
Deposited By: Schwarz, Dr.-Ing. Thorsten
Deposited On:03 Jul 2018 08:49
Last Modified:30 Oct 2023 14:33

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