Passive Bleeding Applied to a Wing in a Roll Maneuver

The leading-edge vortex (LEV) is an inherent feature of high angle-of-attack aerodynamics, impacting the forces acting on the wing. The early development of an LEV produced by a rolling wing can be classified as conical or non-conical (often manifested as an approximately symmetric arch-shaped structure shed from the wing). The classification depends on a non-dimensional velocity gradient or centripetal acceleration parameter, π_rot, which accounts for the effects of both advance ratio and radius of gyration. Dye visualization of the LEV produced by a rolling rectangular plate wing of aspect ratio two was performed for a non-dimensional radius of gyration of 3.25 and advance ratio, J=0.54 (π_rot =0.238), which has been shown to produce a conical vortex structure. Passive bleed was applied by a hole through the wing near the root and leading edge. Visualizations revealed that a significant change occurred that altered the flow from a conical to non-conical behavior. Transport analysis using PIV measurements were performed to understand physical mechanisms governing this fundamental change in flow evolution.