Robustness of the Leading Edge Vortex on Rotating Wings to Unsteady Perturbations

The vast majority of research works on low aspect ratio rotating wings report that, at high angle of attack, the leading edge vortex that forms on the upper surface of the wing is stable. This ‘trick’ is used by insects and auto-rotating seeds, for example, to achieve the desirable amount of lift. Yet, a few experimental studies suggest that leading edge vortices might be unstable under similar, low Rossby number, conditions. While it is unclear what causes vortex shedding in these studies, the present communication explores the sensitivity of leading edge vortex attachment to perturbations of the rotating speed and demonstrates that shedding can be triggered even for very small perturbations, corresponding to wing tip displacements lower than 1% of the wing chord.