Comparison of CFD Prediction and Actual Condition for Wake Effect on an Onshore Wind Farm

Abstract

In order to clarify the wake effect behind wind turbines of a wind farm located on a complex terrain, Computational Fluid Dynamics (CFD) simulations were performed with the WindModeller software, which is a module for wind farm simulation developed by ANSYS. The wake is modelled using an actuator disc model approach which is based on the wind turbine thrust coefficient and wind speed. A WindModeller simulation was carried out for DBK wind farm located on Jeju Island, Korea. The nacelle wind speed data from 15 Hanjin 2MW turbines were collected through the Supervisory Control And Data Acquisition (SCADA) system. The wind data was measured from a 80m tall met mast near the wind farm, which was used as a reference. The WindModeller module simulated the wind speed and turbulence intensity within the terrain with a wind speed of 9.3 m/s and a wind direction of 314 degrees. The wakes from single and multiple turbines were predicted by the WindModeller simulation were compared with the actual wind data from the SCADA system. Then, the wake effect was analyzed with the distance between the wind turbines. As a result, the wake effect predicted by the WindModeller simulation was greater than the actual wake effect. The actual wind speed ratio decreased by 22% and 35% when the turbines were separated with the distances of 3.1 and 5.8 times rotor diameters, respectively. The wake effect behind multiple wind turbines is revealed in this paper.