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.
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