Journal cover Journal topic
Wind Energy Science The interactive open-access journal of the European Academy of Wind Energy
https://doi.org/10.5194/wes-2017-53
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research articles
28 Nov 2017
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Wind Energy Science (WES).
How does turbulence change approaching a rotor?
Jakob Mann, Alfredo Peña, Niels Troldborg, and Søren J. Andersen DTU Wind Energy, Technical University of Denmark
Abstract. For load calculations on wind turbines it is usually assumed that the turbulence approaching the rotor does not change its statistics as it goes through the induction zone. We investigate this assumption using a nacelle-mounted forward-looking pulsed lidar that measures low frequency wind fluctuations simultaneous at distances between one half and three rotor diameters upstream. The measurements show that below rated wind speed the low-frequency wind variance is reduced by up to 10 % at one half rotor diameter upstream and above rated enhanced by up to 20 %. A quasi-steady model that takes into account the change of thrust coefficient with wind speed explains these variations partly. Large-eddy simulations of turbulence approaching an actuator disk model of a rotor support the finding that the slope of the thrust curve influences the low-frequency fluctuations.

Citation: Mann, J., Peña, A., Troldborg, N., and Andersen, S. J.: How does turbulence change approaching a rotor?, Wind Energ. Sci. Discuss., https://doi.org/10.5194/wes-2017-53, in review, 2017.
Jakob Mann et al.
Jakob Mann et al.
Jakob Mann et al.

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Short summary
Turbulence is usually assumed to be unmodified by the stagnation occurring in front of a the wind turbine rotor. All manufacturers assume this in their dynamic load calculations. If this assumption is not true it might bias the load calculations and the turbines might not be designed optimally. We investigate the assumption with a Doppler lidar measuring forward from the top of the nacelle and find small, but systematic changes of the approaching turbulence that depend on the power curve.
Turbulence is usually assumed to be unmodified by the stagnation occurring in front of a the...
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