Effect of the yaw angle on the aerodynamics of two tandem wind turbines by considering a dual-rotor wind turbine in front

The innovative dual-rotor counter-rotating wind turbine (CRWT) shows great importance in the development of offshore wind farms. In this paper, the performance and wake characteristics of the independent CRWT and two tandem wind turbines equipped with a CRWT at different yaw angles were numerically studied using the opensource software SOWFA (Simulator fOr Wind Farm Applications). The actuator line model (ALM) and large-eddy simulation (LES) were used to model wind turbines and turbulent flows. The third generation of vortex identification criterion was used to analyze wake vortex characteristics. The results indicated the auxiliary rotor had a negligible effect on the main rotor in terms of the dominant frequency and fluctuations. In comparison with the rotational blade frequency (BF), it was found that one BF and double BF were equivalent to the dominant frequency of the SRWT and CRWT, respectively. The CRWT suffers a greater velocity deficit and has a faster velocity recovery. In the case of tandem wind turbines, the upstream wind turbine equipped with a CRWT performs minimal influence on the optimal yaw angle of 30. In addition, the effects of the yaw angle on wake center deflection, wake width, and performance fluctuation for the downstream wind turbine were investigated.