Abstract: In recent years, leading-edge protuberances, as a passive method for wing separation control, continue to attract considerable attention in academia. This paper numerically simulates the aerodynamic effects of two lead-ing-edge protuberances with relatively large-scale wavelengths near the critical angle on the aerodynamics of a full-span wing. Compared to the baseline wing, the stall process of the improved wing shapes with larger-scale wave-lengths is slow and stable. Studying the surface flow characteristics, it is found that the wing with serrations of 1.5 times the chord length maintains a single and regular flow pattern both before and after stall, while the surface flow pattern of the wing with serrations of 1 chord length transitions from a single regular flow to a more complex flow composed of multiple flow patterns as the angle increases. A mechanism is proposed to explain this transition in flow patterns, along with two flow combination mechanisms to explain the generation of these two flow patterns.

Key words: Airfoil, stall, leading-edge, flow control, flow pattern