Leading-edge vortex evolution and lift production on rotating wings (invited)

The NATO RTO AVT-202 task group was a collaborative effort to study the fundamental unsteady low Reynolds number aerodynamics of lift production in highly separated flows. Experimental and numerical results are presented here, compiled from four different research groups, to describe the evolution of the flow around a rotating wing experiencing unsteady motion in either pitch or surge and the resulting unsteady lift force. There is excellent agreement, both qualitatively and quantitatively, between the research groups. It was found that wing pitch was the dominant contributor to lift production, and that the magnitude of wing acceleration in surge had relatively little effect. Notably, the introduction of rotational acceleration (as compared to strictly translational motion) did not have a significant effect on the force history. It did, however, result in a different flow topology, namely an attached leading-edge vortex.