Preprint Article Version 1 Preserved in Portico This version is not peer-reviewed

Measurements of high-frequency Atmospheric Turbulence and its Impact on the Boundary Layer of Wind Turbine Blades

Version 1 : Received: 6 June 2018 / Approved: 6 June 2018 / Online: 6 June 2018 (17:49:05 CEST)

A peer-reviewed article of this Preprint also exists.

Schaffarczyk, A.P.; Jeromin, A. Measurements of High-Frequency Atmospheric Turbulence and Its Impact on the Boundary Layer of Wind Turbine Blades. Appl. Sci. 2018, 8, 1417. Schaffarczyk, A.P.; Jeromin, A. Measurements of High-Frequency Atmospheric Turbulence and Its Impact on the Boundary Layer of Wind Turbine Blades. Appl. Sci. 2018, 8, 1417.

Abstract

To gain insight into the differences between onshore and offshore atmospheric turbulence, 2 pressure fluctuations were measured for offshore wind under different environmental conditions. 3 A durable piezo-electric sensor was used to sample turbulent pressure data at 50 kHz. Offshore 4 measurements were performed at 100 m height on Germany’s FINO3 offshore platform in the 5 German Bight together with additional meteorological data provided by Deutscher Wetterdienst 6 (DWD). The statistical evaluation revealed that the stability state in the atmospheric boundary has a 7 large impact on turbulent fluctuations. Therefore, we used higher statistical properties (described 8 by so-called shape factors) to the stability state. Data was classified to be either within the unstable, 9 neutral or stable stratification. We found that in case of stable stratification, the shape factor is 10 mostly close to zero, indicating that a thermally stable environment produces closer-to Gaussian 11 distributions. Non-Gaussian distributions were found in unstable and neutral boundary layer states 12 and an occurrence probability was estimated. Possible impact on laminar-turbulent transition on the 13 blade is discussed with application of so-called laminar aerofoils on wind turbine blades. Use of a 14 cut-off frequency to separate load and aerodynamic turbulence is proposed.

Keywords

Advanced turbulence statistics, piezo-electric flow sensor, atmospheric boundary layer16 stability, laminar-turbulent transition

Subject

Engineering, Energy and Fuel Technology

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