The Effect of Leading and Trailing Edge Protuberances on Aerofoil Performance: Theoretical and Experimental Investigation

This paper presents two-dimensional experimental and numerical studies on the aerodynamic characteristics of modified NACA 634-021 aerofoils with sinusoidal protuberances, on both the leading and trailing edges. Wind tunnel results at Re = 2.4 × 105 showed that the standard NACA 634-021 aerofoil performed better at smaller angles of attack within its pre-stall region as compared to the wavy aerofoils with increasing protuberance amplitude. On the other hand, the wavy aerofoils were found to perform better within the baseline post-stall. The standard K-ε model using the PHOENICS CFD package revealed similar trends to those obtained from the experiments, which validated the numerical procedure. The CFD model also showed that increasing the protuberance wavelength slightly lowers the lift generated at lower angles of attack, but leads to a better performance within the baseline post-stall. Flow analysis using the K- ε model showed that in the case of the wavy aerofoils, flow separation occurs even at small angles of attack in the valleys located behind the leading edge peaks. The numerical analysis also showed that the protuberances located on the leading edge of the aerofoils act as vortex generators. The strength of the vortices increase with angle of attack and flow is energised and pulled over the leading edge peaks, which explains the stall delay characteristics of the wavy aerofoils.