Actuator disc wind turbine wakes simulation: about the dependences on the wind shear conditions

Modelling wind turbine wakes is going to be a fundamental issue in wind energy assessment studies (especially for offshore wind farms) in order to minimize the losses and to maximize the overall energy production. Analytical wake models were successfully used for on-shore wind farm but for off-shore cases CFD (Computational Fluid Dynamics) models seem to give more reliable results. In present work CFD and the actuator disc concept have been applied to simulate the wakes of a group of wind turbines; the force on the rotor was defined according to the thrust coefficient curve supplied by the turbine manufacturer. The numerical model was validated using operational data available from the Horns Rev offshore wind farm. Results demonstrate that the actuator disc model can give useful information on the wakes evolution and that the wind shear conditions can change modestly the energy conversion efficiency but can have a great impact on the wakes propagation.