Fluidic Control of a Wing Tip Vortex

摘要

A novel technique of active wing tip vortex control was studied in a wind tunnel by deflecting a flap mounted at the tip of a semispan NACA 0015 wing model and then modifying the shear layer above the flap by means of zero mass-flux fluidic perturbations. Primary data acquired included surface pressure measurements and particle image velocimetry of the flap region and of the vortex downstream of the wing tip. The shear layer above the flap was particularly responsive to fluidic perturbations, requiring small relative momentum to produce large changes to the layer and consequently the vortex. However, integrated surface pressures showed that deflection of the shear layer, and even eliminating separation completely, had a relatively small effect on the overall aerodynamic loads. Deflection of the shear layer had the effect of moving the vortex outboard and changing the axial velocity at the vortex center from wakelike to jetlike flow. The spanwise deflection of the vortex centroids correlated with the nature of the loading near the wing tip: forward loading corresponded to inboard vortex movement; aft loading corresponded to outboard vortex movement. Variation of the vortex axial velocity was described using the mechanical energy equation where changes from wakelike to jetlike flow were, remarkably, comparable to the magnitude of the freestream velocity.