AERODYNAMIC INVESTIGATION OF TOWER SHADOW EFFECTS ON THE HORIZONTAL AXIAL DUAL-ROTOR WIND TURBINE

In this paper, unsteady numerical simulations for horizontal axis dual-rotor wind turbines with and without a tower were carried out using the actuator line model (ALM) instead of the traditional body-fitted mesh and the large eddy scale (LES) turbulence model to improve the numerical accuracy of the wake. The power coefficient C-p, axial force coefficient C-z and velocity distribution in the near wake were used to validate the accuracy of ALM based on model experimental results of a conventional wind turbine. The results indicated that ALM can accurately predict the aerodynamic performance and wake characteristics which agreed well with the experimental data. Tower shadow had little influence on average aerodynamic performance. But, it can significantly increase the fluctuation amplitude of the dual-rotor wind turbine. Both 1-time RF (rotational frequency) and 2-time RF were nearly noticeable for the dual-wind turbines in the case with a tower, while 2-time RF was obviously remarkable for the dual-rotor wind turbine in the case without a tower. The distribution of the transverse velocity was generally symmetrical in the near wake of 1-5D away from the wind turbine, but the distribution of the longitudinal velocity lost symmetry due to the tower shadow. However, the tower shadow had a negligible effect on the velocity recovery in the far wake.