Leading-edge tubercles in a small-scale H-Darrieus Wind Turbine: Quantification through Morris Elementary Effects

Leading-edge tubercles demonstrated potential to enhance wind turbine performance. However, a comprehensive analysis of the device’s design parameters (amplitude, wavelength, and waviness ratio) influence on turbine performance and their interactions is still needed. Furthermore, for Vertical Axis Wind Turbines (VAWTs), the combined effects of all parameters have never been considered, even though this approach has proven promising for achieving performance gains in Horizontal Axis Wind Turbines (HAWTs). To address these gaps, this study investigates the impact of leading-edge tubercles and their parameter variations on a small-scale, two-bladed NACA 0015 H-Darrieus VAWT using OpenFOAM v2206 and the Morris Elementary Effects method with a radial design to quantitatively assess both the individual and interactive effects of the parameters. The results indicate that all three parameters are interacting variables. While all tested configurations at a Tip–Speed Ratio (TSR) of 2.29 reduced equipment performance, we demonstrated that under varied operational conditions, tubercles can increase the power coefficient, up to 8.69%. Subsequent analysis of the vorticity field around the blade revealed that the vortices generated by the tubercles can produce two opposing effects. In detrimental configurations, intensification of dynamic stall and premature flow separation, whereas in beneficial configurations, the device mitigated tip vortex shedding.