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Effect of winglet geometry on horizontal axis wind turbine performance

Winglets (WLs) have recently been used to improve the performance of horizontal axis wind turbine (HAWT). The WL geometry is a key parameter for diverging blade tip vortices away from turbine blades and reducing induced drag. The present study focuses on the effect of winglet height (H) and toe angle (αw) on the turbine performance. The performance of a three‐bladed rotor of 1 m diameter with SD8000 aerofoil is numerically investigated using ANSYS 17.2 CFD on a polyhedral mesh. The model is hence validated by comparing results for power coefficient (Cpw) with experimental values available in the literature. Four different values of H are considered while keeping αw constant at 0°. H of 0.8%R is proved to be the best height for performance enhancement. It increases Cpw by 2.4% at tip speed ratio λ = 7. The toe angle effect is studied for upwind and downwind WLs. The results show that Cpw increases as αw increases up to αw = +20° at all values of λ. Cpw increases by 6% at λ = 7. Downwind WL always reduces Cpw. The present results are well explained by the resulting vectors map near the blade tip. Using WL with the optimum H and αw, causes 6% increase in Cpw as compared to rotor without WL.