Numerical Investigations of Wind Turbine Wakes under Neutral and Convective Atmospheric Stability Conditions

Abstract

Large-eddy simulation (LES) technique combined with the actuator line model (ALM) is employed to investigate the characteristics of wind turbine wakes under both neutral and convective atmospheric boundary layer (ABL) stability regimes. Turbulence properties of the incoming wind that due to thermal stratification are collected by the precursor ABL simulation, and then are used to initialize the flow field upstream of a single wind turbine. For the neutral case, comparison with the wind tunnel experiments shows an acceptable agreement in the wake velocity distribution and turbulence characteristics, which proves the accuracy of the employed numerical methods to some extent. Besides, numerical results are compared between two atmospheric conditions. Through the evaluations of the velocity deficit and turbulent intensity in the wake area, it is shown that the ABL stability has a significant effect on the wake development; and particularly, a more rapid wake recovery is observed in the convective condition. These results suggest that atmospheric thermal stability is crucial to be taken into account in the prediction of wake effects and in the design of wind farms.