Three dimensional visualization of leading edge vortex structure of a pitching and rolling wing in forward flight*

Plenoptic particle image velocimetry is used to visualize the three dimensional vortex topology of an aspect-ratio 2.0 flat-plate wing undergoing independent and simultaneous pitching and rolling motions in the presence of a free stream with Reynolds number of 10,000.  The dimensionless pitch rate, k, and advance ratio, J, was varied from 0.2 to 0.5 and 0.5 to 1.25, respectively.  Three-dimensional, three-component velocity fields acquired at different phases of the motion depict a leading edge vortex (LEV) structure that initially grows and then sheds as the pitch angle increases with three-dimensional details of the LEV topology highly dependent on the parameters given above.  In the simultaneous pitch and roll case, features of both pure roll and pure pitch vortex topologies are present with their relative strength dependent on a parameter, π_rot, that combines the competing influences of k and J.