The flow field of the wing tip vortex, which shed from a rectangular wing, is surveyed by a seven holes probe in a low speed wind tunnel.

Tip vortex goes downstream outward along the span direction, and the induced drag of the wing decreases.

In the experiment, a simplified aircraft model (with tail wing) is employed to construct a 4-vortex wake system consisting of a pair of tip vortices and a pair of counter rotating tail plane vortices.