Excitation of instabilities in the wake of an airfoil by means of active winglets☆

Strong wake vortices that develop behind every aircraft as a byproduct of lift production pose a threat where aircraft fly in close staggering such as in the vicinity of airports. One approach to alleviate these vortex wakes is the use of high lift systems or control surfaces of the wing to create an unstable vortex system. The inherent instability of this vortex system shall then lead to an accelerated decay of the vortex wake, triggered for example by a periodic motion of the control surfaces. In the work presented here a simple wing model with winglets able to produce a vortex system of up to six distinct vortices is investigated in towing tank experiments. Theoretical studies show that these vortex systems potentially have a high degree of instability. By means of active oscillation of rudders integrated into the winglets, these vortex systems are to be excited to initiate an accelerated decay of the vortices. It is shown that configurations exist which exhibit strong instabilities, that lead to a significantly lower hazard level behind the vortex generating wing, even when not actively excited. However, an additional oscillation does not seem to accelerate decay of these vortex systems in relation to the statical reference case.