Active Management of Flap-Edge Trailing Vortices*
4th Flow Control Conference, Seattle, Washington, June 23-26, 2008 Active Management of Flap-Edge Trailing Vortices* David Greenblatt Technion – Israel Institute of Technology, Haifa, Israel Chung-Sheng Yao† NASA Langley Research Center, Hampton VA, USA Stefan Vey,‡ Oliver C. Paschereit¶ Berlin University of Technology, Berlin, Germany Robert Meyer§ German Aerospace Center (DLR), Berlin, Germany The vortex hazard produced by large airliners and increasingly larger airliners entering service, combined with projected rapid increases in the demand for air transportation, is expected to act as a major impediment to increased air traffic capacity. Significant reduction in the vortex hazard is possible, however, by employing active vortex alleviation techniques that reduce the wake severity by dynamically modifying its vortex characteristics, providing that the techniques do not degrade performance or compromise safety and ride quality. With this as background, a series of experiments were performed, initially at NASA Langley Research Center and subsequently at the Berlin University of Technology in collaboration with the German Aerospace Center. The investigations demonstrated the basic mechanism for managing trailing vortices using retrofitted devices that are decoupled from conventional control surfaces. The basic premise for managing vortices advanced here is rooted in the erstwhile forgotten hypothesis of Albert Betz, as extended and verified ingeniously by Coleman duPont Donaldson and his collaborators. Using these devices, vortices may be perturbed at arbitrarily long wavelengths down to wavelengths less than a typical airliner wingspan and the oscillatory loads on the wings, and hence the vehicle, are small. Significant flexibility in the specific device has been demonstrated using local passive and active separation control as well as local circulation control via Gurney flaps.
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