Preprint Article Version 1 This version is not peer-reviewed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.

Journal reference: Appl. Sci. 2018, 8, 1417
DOI: 10.3390/app8091417

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.

Subject Areas

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

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