The effect of Whitcomb winglets and other wingtip modifications on wake vortices

Wind tunnel experiments have been conducted on six different wingtip configurations to determine their wake vortex characteristics. The trailing wingtip vortex was probed by a 1/8 inch diameter five hole yawhead pressure probe in the VPI & SU Stability Wind Tunnel. The vortex tangential and axial velocity profiles are compared at five and twenty chord lengths downstream.

Primary focus is placed on the Whitcomb winglet and its individual components, the upper winglet alone and the lower winglet alone. It is shown that the Whitcomb winglet and the upper winglet configuration both produce two distinct vortices of the same rotation. The maximum tangential velocity in each vortex is about 64 percent less than that produced by a conventional wingtip configuration. The axial velocity profiles exhibit strong velocity deficits throughout the vortex core.

Aerodynamic force tests were conducted to compare the lift and drag characteristics of the wingtip configurations. Both the Whitcomb winglet and the upper winglet configuration have a remarkable ability to increase the lift-drag ratio and reduce the drag coefficient.