Measurements of the Evolution of the Wake and Tip Vortex of a Control Surface Undergoing Periodic Motion

A wind tunnel investigation has been carried out into the downstream wake of a floor mounted control surface undergoing periodic motion. The control surface tested has a rectangular planform and geometric aspect ratio of 1. Results are presented for tests at a Reynolds Number of 560,000 with extensive pitot-static axial wake surveys and use of Particle Image Velocimetry, PIV, to study the behaviour of the tip vortex. PIV results are given for one axial station at 55% x/c downstream of the trailing edge. The steady results are analysed to show the size and strength of the tip vortex as a function of angle of attack. PIV results are taken at four stages in a periodic oscillation corresponding to minimum, maximum and mean angles of attack. A time dependent behaviour is clearly observed in the strength and location of the tip vortex.