Transport Mechanisms Governing initial Leading-Edge Vortex Development on a Rolling Wing

The formation and evolution of Leading Edge Vortices (LEVs) are ubiquitous in natural fliers and maneuvering wings, and have a profound impact on aerodynamic loads. The formation of an LEV is experimentally investigated using plenoptic PIV on a rolling flat-plate wing of aspect-ratio 2, and dimensionless advance coefficients of J=U_∞/(R_g Ω_x) of 0.54 and 1.36 at a Reynolds number of 10⁴ . The sources, sinks and rotational augmentation of the vorticity field that contribute to the growth and evolution of the LEV are investigated over the wing. The balances of fluxes for the J=0.54 case varies in time and in spanwise position, the shear layer flux is large for the inboard portion of the wing and decreases with increasing spanwise position, while the spanwise convective flux starts off small on the inboard portion of the wing and increases with an increasing roll angle. This is in the area where a conical LEV is observed. The J=1.36 evolution is markedly different, the shear layer flux and the spanwise convective flux remain constant during the motion and in the spanwise direction.