Effect of vortex generator orientation on wind turbines considering the three-dimensional rotational effect

Abstract

A three-dimensional rotational effect (TDRE) is created in the rotating wind turbines. A TDRE generates a spanwise velocity on the blade surface and changes the inflow angle of vortex generators (VGs) mounted on the blades. The optimal design of VGs should consider the TDRE to improve the aerodynamic performance of a wind turbine. This study analyzes the physical mechanisms of counter-rotating (CtR) and co-rotating (CoR) VGs on a flat plane at different incoming wind directions. Then, the behaviors of CtR and CoR VGs affected by the TDRE were examined on a National Renewable Energy Laboratory (NREL) phase VI wind turbine to find the fit spacing. The computational fluid dynamics studies were validated by experimental data. The results showed that VGs can improve the output power of the wind turbine and delay airflow separation on the blade section. Due to the inclined inflow generated by the TDRE, CtR VGs produced asymmetric vortices pairs behind them, and the effect of CtR VGs was weakened due the substantially decreased strength of one VG. In contrast, CoR VGs formed the same inflow angles under the spanwise velocity, generated more steady shedding vortices, and were relatively more advantageous than CtR VGs. In addition, when the spacing of CoR VGs was z = 3h, the attached flow area on the blade surface was about 10% larger than that when z = 2h.