Aerodynamic control of low-reynolds-number airfoil with leading-edge protuberances

This paper presents an experimental investigation of the control of airfoil aerodynamics at a low Reynolds number of 5 × 104 within a wide range of attack angle α using a leading-edge-protuberance technique. The essence of the technique is to manipulate flow around the airfoil by replacing the straight leading edge of a baseline airfoil with a sinusoidal wavy airfoil. Whereas the lift and drag forces and the lift-to-drag ratio were measured using a threecomponent force balance, the flow was mainly measured using a particle-image velocimetry. The sinusoidal protuberances effectively suppressed airfoil stall, and the corresponding aerodynamic performance was impaired to some extent. Meanwhile, control significantly improved the airfoil aerodynamics in the poststall α region, for example, 16 < α < 70 deg, leading to a maximum 25.0 and 39.2% increase in lift coefficient and lift-to-drag ratio, respectively, and a maximum 20.0% decrease in drag coefficient. The protuberances may influence control performance in a similar way with low-profile vortex generators. The flow physics behind the observations were discussed in detail.