Abstract
Results from Large-Eddy Simulations using the actuator line technique have been validated against experimental results. The experimental rotor wake, which forms the basis for the comparison, was studied in a recirculating free-surface water channel, where a helical vortex was generated by a single-bladed rotor mounted on a shaft. An investigation of how the experimental blade geometry and aerofoil characteristics affect the results was performed. Based on this, an adjustment of the pitch setting was introduced, which is still well within the limits of the experimental uncertainty. Excellent agreement between the experimental and the numerical results was achieved concerning the circulation, wake expansion and pitch of the helical tip vortex. A disagreement was found regarding the root vortex position and the axial velocity along the centre line of the tip vortex. This work establishes a good base for further studies of more fundamental stability parameters of helical rotor wakes.
Highlights
Studies focusing on understanding the stability properties of the wakes generated by wind turbine rotors have been intensified during the last decade
In 2010, Ivanell et al [3] performed a numerical investigation of the tip spiral instability of a wind turbine wake
We show, as an example, the experimental evolution of the wake radius and various corresponding numerical results obtained for different twist offsets β
Summary
Studies focusing on understanding the stability properties of the wakes generated by wind turbine rotors have been intensified during the last decade. In 2010, Ivanell et al [3] performed a numerical investigation of the tip spiral instability of a wind turbine wake. Experimental studies of wind turbine tip spiral instabilities have been carried out by Leweke et al [6] and Bolnot [7]. The stability results by Leweke et al [6] agree well with the results of Ivanell et al [3] and Sarmast et al [4]. No study known to the authors have been performed to make a detailed comparison between experiments and simulations considering the same configuration, with focus on tip spiral instability
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