Effect of a Single Leading-Edge Protuberance on NACA 634-021 Airfoil Performance

April 10-15, 2016 Abstract Leading-edge protuberances on airfoils or wings have been considered as a viable passive control method for flow separation. In this paper, the aerodynamic performance of a modified airfoil with a single leading-edge protuberances was investigated and compared with the baseline NACA 634-021. Spalart-Allmaras turbulence model was applied for numerical simulation and smoke flow was used for experimental visualization. Compared to the sharp decline of baseline lift coefficient, the stall angle of the modified foil is advanced and the decline of lift coefficient becomes mild. The post-stall performance of the modified airfoil is also improved. The attached flows along the peak of the protuberance help improving the total performance of the airfoil. Asymmetrical flows along the spanwise direction are observed on the modified airfoil, which may be responsible for the performance decline at pre-stall attack angles. The formation mechanism and suppression method of the symmetry breaking phenomenon should be investigated more deeply in the future to guide the practical application of the passive control method. .