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Open AccessArticle

Investigation of Laminar–Turbulent Transition on a Rotating Wind-Turbine Blade of Multimegawatt Class with Thermography and Microphone Array

Kiel University of Applied Sciences, Grenzstrasse 3, D-24149 Kiel, Germany
Bremen Institute for Metrology, Automation and Quality Science, University of Bremen, D-28359 Bremen, Germany
Deutsche WindGuard Engineering GmbH, D-27580 Bremerhaven, Germany
DLR, German Aerospace Center, Institute of Aerodynamics and Flow Technology, D-37073 Göttingen, Germany
Flensburg University of Applied Sciences, Kanzleistrass 91-93, D-24943 Flensburg, Germany
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Energies 2019, 12(11), 2102;
Received: 18 April 2019 / Revised: 21 May 2019 / Accepted: 23 May 2019 / Published: 1 June 2019
(This article belongs to the Special Issue Recent Advances in Aerodynamics of Wind Turbines)
Knowledge about laminar–turbulent transition on operating multi megawatt wind turbine (WT) blades needs sophisticated equipment like hot films or microphone arrays. Contrarily, thermographic pictures can easily be taken from the ground, and temperature differences indicate different states of the boundary layer. Accuracy, however, is still an open question, so that an aerodynamic glove, known from experimental research on airplanes, was used to classify the boundary-layer state of a 2 megawatt WT blade operating in the northern part of Schleswig-Holstein, Germany. State-of-the-art equipment for measuring static surface pressure was used for monitoring lift distribution. To distinguish the laminar and turbulent parts of the boundary layer (suction side only), 48 microphones were applied together with ground-based thermographic cameras from two teams. Additionally, an optical camera mounted on the hub was used to survey vibrations. During start-up (SU) (from 0 to 9 rpm), extended but irregularly shaped regions of a laminar-boundary layer were observed that had the same extension measured both with microphones and thermography. When an approximately constant rotor rotation (9 rpm corresponding to approximately 6 m/s wind speed) was achieved, flow transition was visible at the expected position of 40% chord length on the rotor blade, which was fouled with dense turbulent wedges, and an almost complete turbulent state on the glove was detected. In all observations, quantitative determination of flow-transition positions from thermography and microphones agreed well within their accuracy of less than 1%. View Full-Text
Keywords: boundary-layer transition; wind turbine; thermography; aerodynamic glove boundary-layer transition; wind turbine; thermography; aerodynamic glove
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Reichstein, T.; Schaffarczyk, A.P.; Dollinger, C.; Balaresque, N.; Schülein, E.; Jauch, C.; Fischer, A. Investigation of Laminar–Turbulent Transition on a Rotating Wind-Turbine Blade of Multimegawatt Class with Thermography and Microphone Array. Energies 2019, 12, 2102.

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