Prediction of Aerodynamic Loadings and Power Productions of Wind Turbines in Wake by Numerical Simulation

In this paper, the Large Eddy Simulation coupled with the Actuator line (LES-AL) method is employed to analyze the performance of the downstream wind turbine under varying inflow conditions. A direct LES, which solves the flow physics around turbine blades using exact three-dimensional blade geometries, is carried out to predict the aerodynamic loadings and output powers of the downstream turbines by prescribing the wake profiles predicted by LES-AL simulation as the inflow boundary conditions. The upstream tower shadow effect is presented in this study by carrying out two simulations with no tower wake and real tower wake inflow conditions. The LES results show that both the power and aerodynamic loading components fluctuate periodically due to the presence of upstream tower. In additional, an additional force component is exerted on the downstream wind turbine in the vertical direction (z direction). The increase in velocity deficit in wake in behind the downstream turbine is due to a sequence of momentum extraction by the wind turbines. The tower shadow effect accumulates and generates lower velocity regions in wake, and the low velocity regions shift due to the rotational motion of wake vortex. The development of the asymmetric and velocity deficit region has the potential to generate more unstable power output and fatigue loading on turbines in further downstream.