Excitation of Instabilities in the Wake of a Wing with Winglets

Abstract

This paper describes experimental investigations of possibilities to destabilize the vortex wake behind an airfoil by using winglets with integrated rudders. These rudders can be deflected statically, as well as oscillated periodically around their static deflection. The oscillation is intended to excite short-wavelength instabilities inherent in the vortex system to provoke an accelerated decay of the vortices. The used model also comprises deflectable ailerons and can be equipped with a pair of trailing edge flaps to modify the vortex system. Quantitative wake investigations by Particle Image Velocimetry have been conducted up to 43 spans behind the wing model in a water towing tank. Results show a markedly earlier decay of the vortex system and abatement of induced rolling moments in the wake for certain rudder configurations in comparison to the clean airfoil configuration. However, the oscillation of the winglet rudders did not lead to a further acceleration of vortex decay compared to the statical case in the frame of the experiments conducted here.