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

Torben Reichstein, Alois Peter Schaffarczyk, Christoph Dollinger, Nicolas Balaresque, Erich Schülein, Clemens Jauch and Andreas Fischer
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Torben Reichstein: Kiel University of Applied Sciences, Grenzstrasse 3, D-24149 Kiel, Germany
Alois Peter Schaffarczyk: Kiel University of Applied Sciences, Grenzstrasse 3, D-24149 Kiel, Germany
Christoph Dollinger: Bremen Institute for Metrology, Automation and Quality Science, University of Bremen, D-28359 Bremen, Germany
Nicolas Balaresque: Deutsche WindGuard Engineering GmbH, D-27580 Bremerhaven, Germany
Erich Schülein: DLR, German Aerospace Center, Institute of Aerodynamics and Flow Technology, D-37073 Göttingen, Germany
Clemens Jauch: Flensburg University of Applied Sciences, Kanzleistrass 91-93, D-24943 Flensburg, Germany
Andreas Fischer: Bremen Institute for Metrology, Automation and Quality Science, University of Bremen, D-28359 Bremen, Germany

Energies, 2019, vol. 12, issue 11, 1-21

Abstract: 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%.

Keywords: boundary-layer transition; wind turbine; thermography; aerodynamic glove (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2019
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