Darrieus Vertical Axis Wind Turbine (VAWT) Performance Enhancement by Means of Gurney Flap

Abstract

This study investigates the aerodynamic effect of Gurney flaps (GFs) of different heights on the performance of a Darrieus vertical axis wind turbine (VAWT). Through numerical simulations, the performance of a baseline airfoil is compared against configurations with GFs of 0.5%c, 1%c, and 1.5%c chord lengths across a range of tip-speed ratios (TSRs). Results identify the 0.5%c GF as the optimal configuration, providing consistent power enhancement across all tested conditions, unlike the taller flaps which showed inconsistent or negative effects. This optimal configuration achieved a peak power coefficient (Cp) of 0.366 at TSR = 2.0, a 3.73% improvement over the baseline, and critically, enhanced the low-speed power by 6.30% at TSR = 0.5, improving the turbine’s self-starting capability. Flow field analysis reveals a dual-benefit mechanism for this superior performance: at low TSRs, the GF delays flow separation during the upwind pass to increase lift, while at higher TSRs, it effectively manages the wake during the downwind pass to reduce drag and mitigate negative torque. The study concludes that the 0.5%c GF strikes an optimal balance between lift augmentation and drag.