Experimental investigation of the potential of wedge flaps for improving the aerodynamic performance of a straight-bladed vertical axis wind turbine

• NACA0021 is equipped with wedge-flaps (WF) for aerodynamic performance enhancement. • The optimized rotor blade with WF is applied to vertical axis wind turbine (VAWT) • The comparison of the modified VAWT with clean case was carried out. • Experimental results show that WFs can enhance the performance of straight-bladed VAWTs. Vertical-axis wind turbines (VAWTs), such as the Darrieus configuration, offer a clean renewable energy source that can reduce reliance on fossil fuels. Compared with horizontal-axis wind turbines (HAWTs), VAWTs present several advantages. However, their performance is constrained by inherent limitations, including dynamic stall, wake rotation effects, and self-starting difficulties, which hinder their commercial viability. Passive flow control techniques, such as adding a wedge flap (WF) to the trailing edge of rotor blades, offer a potential solution. This study examines the performance of straight-bladed VAWTs (SB-VAWTs) with and without optimized WFs. Rotor blades were designed, fabricated, and tested in a wind tunnel under varying wind speeds and loading conditions. Results showed that adding a WF significantly enhances the power coefficient ( C p ) across different wind speeds. Maximum C p and electrical power output increased by 11% at 5 m/s and up to 20% at 13 m/s compared to clean VAWTs. Furthermore, C p -TSR curves became flatter, indicating improved stability and reduced sensitivity to sudden wind speed changes. The WF demonstrates potential as a passive flow control device, enhancing VAWT performance while maintaining adaptability. With proper dimensioning, WFs could be integrated into new turbines or retrofitted onto existing ones, making them a promising option for renewable energy systems.