Effect of Chordwise Slots on Aerodynamic Efficiency and Wingtip Vortex

The balance of induced and parasite drag and the rollup process of wingtip vortex from a NACA 0012 wing was affected by allowing the freestream to pass through chordwise slots connecting the leading and trailing edge of the wing at multiple spanwise locations. Three wing configurations, one with 8 slots equally spaced, the second with 11 slots elliptically spaced (resembling lift distribution), and the third without any slots were tested at the University of Dayton Low-Speed Wind Tunnel (UD-LSWT). The force-based experiment indicated similar lift coefficient for all three cases at lower angles of attack even with the loss of several stagnation points on the slotted wings. However, the parasitic drag coefficient (obtained through momentum deficit profiles in the wake) of wings with 8 slots equally spaced and 11 slots elliptically spaced were greater than the baseline. Even though the aerodynamic efficiency is reduced by little percentage, significant reductions in wingtip vortex azimuthal velocity, circulation, and turbulent intensity were observed in the slotted wing when compared with the baseline. The reduction in the wingtip vortex properties was attributed to the increased interaction of the wingtip vortex and the free shear layer.