Articles | Volume 1, issue 1
Wind Energ. Sci., 1, 41–53, 2016
Wind Energ. Sci., 1, 41–53, 2016

Research article 11 Apr 2016

Research article | 11 Apr 2016

Full-field assessment of wind turbine near-wake deviation in relation to yaw misalignment

Juan José Trujillo1, Janna Kristina Seifert1, Ines Würth2, David Schlipf2, and Martin Kühn1 Juan José Trujillo et al.
  • 1ForWind – University of Oldenburg, Institute of Physics, Ammerländer-Heerstr. 136, 26129 Oldenburg, Germany
  • 2Stuttgart Wind Energy at University of Stuttgart, Institute of Aircraft Design, Allmandring 5B, 70569 Stuttgart, Germany

Abstract. Presently there is a lack of data revealing the behaviour of the path followed by the near wake of full scale wind turbines and its dependence on yaw misalignment. Here we present an experimental analysis of the horizontal wake deviation of a 5 MW offshore wind turbine between 0.6 and 1.4 diameters downstream. The wake field has been scanned with a short-range lidar and the wake path has been reconstructed by means of two-dimensional Gaussian tracking. We analysed the measurements for rotor yaw misalignments arising in normal operation and during partial load, representing high thrust coefficient conditions. We classified distinctive wake paths with reference to yaw misalignment, based on the nacelle wind vane, in steps of 3° in a range of ±10.5°. All paths observed in the nacelle frame of reference showed a consistent convergence towards 0.9 rotor diameters downstream, suggesting a kind of wake deviation shift. This contrasts with published results from wind tunnels which in general report a convergence towards the rotor. The discrepancy is evidenced in particular in a comparison which we performed against published paths obtained by means of tip vortex tracking.

Short summary
We present the analysis of the trajectories followed by the wind, in the immediate vicinity, behind an offshore wind turbine and their dependence on its yaw misalignment. We apply wake tracking on wind fields measured with a lidar (light detection and ranging) system located at the nacelle of the wind turbine and pointing downstream. The analysis reveals discrepancies of the estimated mean wake paths against theoretical and wind tunnel experiments using different wake-tracking techniques.