The aerodynamic imbalance and asymmetric wake of a horizontal-axis wind turbine in the wind shear field

The characteristics of the aerodynamic force and the near wake of the full-scale NREL 5 MW wind turbine are numerically investigated, considering the effects of wind shear and yaw angles. The results show that yaw operation reduces the average aerodynamic loads on blades, while the alleviation of stall effects in high-wind-speed regions significantly alters the pressure distribution on blade surface, amplifying the fluctuation of aerodynamic coefficients. The combined influence of the tangential component of incoming flows and centrifugal forces generates dynamic spanwise flow, which leads to a significant asymmetry of the thrust and torque on blades during the downward rotations, compared to the upward rotations. Furthermore, the wind shear accompanying with the streamwise rotating wake induce pronounced asymmetric distribution of the streamwise velocity in the near wake. Finally, a three-dimensional asymmetric double-Gaussian wake model (3DAG model) is developed to accurately predict the near-wake velocity profile under wind shear conditions.