Preprint Article Version 1 This version is not peer-reviewed

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

Version 1 : Received: 18 April 2019 / Approved: 19 April 2019 / Online: 19 April 2019 (11:58:41 CEST)

A peer-reviewed article of this Preprint also exists.

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. 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.

Journal reference: Energies 2019, 12, 2102
DOI: 10.3390/en12112102

Abstract

Knowledge about laminar-turbulent transition on operating multi-megawatt wind turbine 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. The accuracy however, still is an open question, so that an aerodynamic glove known from experimental research on aero-planes was used to classify the boundary-layer state of a 2 megawatt wind turbine blade operating in the orthern part of Schleswig-Holstein, Germany. State-of-the-art equipment for measurering static surface pressure was used for monitoring the lift distribution. To distinguish 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 (from 0 to 9 rpm) extended, but irregularly shaped regions of a laminar boundary layer were observed which 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, a 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 the flow transition positions from thermography and microphones agree well within their accuracy.

Subject Areas

boundary layer transition; wind turbine; thermography; aerodynamic glove

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