Preprints
https://doi.org/10.5194/wes-2021-95
https://doi.org/10.5194/wes-2021-95

  23 Aug 2021

23 Aug 2021

Review status: this preprint is currently under review for the journal WES.

Field measurements of wake meandering at a utility-scale wind turbine with nacelle-mounted Doppler LiDARs

Peter Andreas Brugger1, Corey D. Markfort2, and Fernando Porté-Agel1 Peter Andreas Brugger et al.
  • 1Wind Engineering and Renewable Energy Laboratory (WiRE), École Polytechnique Fedérale de Lausanne (EPFL), 1015 Lausanne, Switzerland
  • 2IIHR-Hydroscience & Engineering, Dept. of Civil and Environmental Engineering, The University of Iowa, Iowa City, IA 52242, USA

Abstract. Wake meandering is a low-frequency oscillation of the entire wind turbine wake that can contribute to power and load fluctuations of downstream turbines in wind farms. Field measurements of two Doppler LiDARs mounted on the nacelle of a utility-scale wind turbine were used to investigate relationships between the inflow and the wake meandering as well as the effect of wake meandering on the temporally averaged wake. A correlation analysis showed a linear relationship between the instantaneous wake position and the lateral velocity that degraded with the evolution of the turbulent wind field during the time of downstream advection. A low-pass filter proportional to the advection time delay is recommended to remove small scales that become decorrelated even for distances within the typical spacing of wind turbine rows in a wind farm. The results also showed that the velocity at which wake meandering is transported downstream was slower than the inflow wind speed, but faster than the velocity at the wake center. This indicates that the modelling assumption of the wake as an passive scalar should be revised in the context of the downstream advection. Further, the strength of wake meandering increased linearly with the turbulence intensity of the lateral velocity and with the downstream distance. Wake meandering reduced the maximum velocity deficit of the temporally averaged wake and increased its width. Both effects scaled with the wake meandering strength. Lastly, we found that the fraction of the wake turbulence intensity that was caused by wake meandering decreased with downstream distance contrary to the wake meandering strength.

Peter Andreas Brugger et al.

Status: open (until 04 Oct 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Peter Andreas Brugger et al.

Peter Andreas Brugger et al.

Viewed

Total article views: 182 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
124 57 1 182 1 0
  • HTML: 124
  • PDF: 57
  • XML: 1
  • Total: 182
  • BibTeX: 1
  • EndNote: 0
Views and downloads (calculated since 23 Aug 2021)
Cumulative views and downloads (calculated since 23 Aug 2021)

Viewed (geographical distribution)

Total article views: 176 (including HTML, PDF, and XML) Thereof 176 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 23 Sep 2021
Download
Short summary
Wind turbines create a wake of reduced wind speeds downstream of the rotor. The wake has not necessarily a straight, pencil-like shape, but can meander similar to a smoke plume. We investigated this wake meandering and observed that the downstream transport velocity is slower than the wind speed contrary to previous assumptions, and that the evolution of the atmospheric turbulence over time impacts wake meandering on distances typical for the turbine spacing in wind farms.