Numerical analysis of Gurney flap performance on a VAWT: highlighting dynamic flow interaction

This study employs two-dimensional computational fluid dynamics to investigate how a trailing-edge Gurney flap affects vertical axis wind turbine (VAWT) performance. The numerical model was validated against established benchmark data, confirming its accuracy. Simulations compared a three-bladed VAWT with NACA 64(2)-415 airfoils in two configurations—clean blades versus those with a 1% chord Gurney flap—across tip speed ratios (TSRs) from 0.5 to 2.5. Results revealed striking TSR-dependent performance variations. The Gurney flap dramatically improved power output at TSR 1.0, delivering an 83.5% increase in power coefficient. It also enhanced performance at TSR 0.5 (5.8% increase) and TSR 2.0 (3.1% increase), while maintaining comparable performance at TSRs 1.5 and 2.5 (differences below 0.5%). Instantaneous moment analysis revealed that the Gurney flap significantly improves torque generation during critical portions of the rotation cycle, particularly at moderate TSRs where VAWTs typically underperform. These findings demonstrate that Gurney flaps can substantially enhance VAWT performance across most operating conditions, with particularly remarkable benefits at TSR 1.0. This challenges conventional understanding derived from static airfoil studies and highlights the complex, dynamic nature of flow control in rotating systems.