Active-control system for breakup of airplane trailing vortices

Wing control surfaces are used to trigger the breakup of trailing vortices behind aircraft in a flaps-down configuration. In the near field of the aircraft there are multiple pairs of vortices, which admit new instability mechanisms that do not exist on a single pair of vortices. A periodic motion of the control surfaces is used to introduce a unique form of perturbation that is amplified in the multiple vortex-pair system but conserves total circulation, lift, and rolling moment. Growth of the perturbations leads to the periodic pinching of the starboard and port vortices into a series of vortex rings. The concept is demonstrated using numerical simulations and towing-tank experiments. Results show that the system breaks up the trailing vortices more rapidly than a comparable excitation of the Crow instability on a single pair of vortices. The overall effectiveness of the system depends on the airplane configuration, namely, details of the flap system and the horizontal tail.