Numerical study of aerodynamic performance of horizontal axis dual-rotor wind turbine under atmospheric boundary layers

The use of horizontal axis dual-rotor wind turbine (DRWT) is a new strategy to enhance the capture rate of wind energy and increase the performance of wind farms. An actuator line model (ALM) and large eddy simulation(LES) are introduced to investigate the aerodynamic performance of DRWT, and its effects on downstream turbines under convective atmospheric boundary layer (CBL) and neutral atmospheric boundary layer (NBL). The results conclude that the dominant vibration frequencies of the power production for the front rotor of DRWT are nearly the same as those of the single-rotor wind turbine (SRWT) under both NBL and CBL, but the vibration amplitude is slightly higher. The strength and dominant frequencies of yaw moment (Myaw) for the front rotor of DRWT are almost the same as those of the SRWT in both NBL and CBL flows, while the results of blade-root out-of-plane bending moment (Moop) are different. There are obvious differences in wake development and wake meandering between the DRWT and the SRWT. For three turbines cases, the total power production is increased respectively by 3.3% and 3% under NBL and CBL at a tandem spacing of 5D when the DRWT is placed in the first row, while the results increase to 5.5% and 4.4% at a tandem spacing of 9D. The stability of Myaw and Moop of second-row turbine located 5D downstream behind the DRWT under both NBL and CBL and Moop of all turbines located behind the DRWT in three tandem spacings (5D, 7D, 9D) under CBL are deteriorated compared with those located behind the SRWT.