Dynamics of triple vortex system on a supercritical wing-tip geometry

The system of wing-tip vortices and its dynamics on a cantilever wing with a supercritical airfoil profile under low Mach number and moderate angle of attack were analyzed. The results of Particle Image Velocimetry (PIV) in a wind tunnel reveal that in addition to the well-documented primary vortex on the tip surface and the secondary vortex on the suction surface, the strong camber of the airfoil near the trailing edge generates the additional tertiary vortex from the shear layer of the primary vortex. These tip vortices co-rotate in a helical profile, becoming similar in size and vorticity level as they are convected past the trailing edge. A computational validation was conducted with Large Eddy Simulation (LES) on the identical wing tip geometry, showing good agreement. The dynamics of these vortices were analyzed through the Proper Orthogonal Decomposition (POD) of the flow field, which indicates the presence of high-energy vortex displacement modes. The POD modes show that the displacement of the secondary vortex has low correlation with that of the primary and tertiary vortex. The unsteady surface pressure was measured to find the dominant frequency of fluctuations in each of the tip vortices, and they are shown to have a slight correlation with the angle of attack.