Numerical investigations of wake flows of counter-rotating wind turbines in shear inflows

Wake effect” is a universal phenomenon in large-scale wind farms, which will adversely affect the benefit of wind farms. In this study, we adopt a tandem arrangement of two wind turbines to investigate a new wake effect restraining strategy called “Counter-Rotating Wind Turbine (CRWT) system” based on actuator line model and large eddy simulation. From the numerical results, the power output of the downstream wind turbine in counter-rotating configuration increased compared with co-rotating configuration. As the longitudinal spacing increases, the fluctuation of the power output of the downstream wind turbine increases, and the rotation direction has little effect on it. The yaw moment ( and blade-root out-of-plane bending moment ( M_oop M_yaw ) ) increase with increasing longitudinal spacing due to the local wake meandering caused by the amplified unstable shed vortex, but the rotation direction of the downstream wind turbine has little effects on them. Moreover, the low-speed shaft torque ( ) of the downstream wind turbine with the M_lss reverse rotation strategy increases when the longitudinal spacing is closer, which is consistent with the power output result.