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Fazle Hussain
Departments of Mechanical Engineering, Physics, and Geosciences
University of Houston

September 24, 2010
Foothills Laboratory 2, Room 1022
Lecture 1:30pm

The Looming Crisis in Air Traffic Capacity -Can Vortex Dynamics Help?

The air traffic capacity is projected to be tripled by 2025, demanding a tripling of runways at major airports of the world. Safe aircraft separation to avoid wake hazard is not only already a challenge during takeoffs and landings, but will become a major problem also during cruise in the crowded skies. We propose a method of breaking up the trailing vortices and inducing their rapid decay so that separation between aircraft can be significantly reduced. We study via direct numerical simulation the evolution of a vortex column embedded in fine-scale turbulence, and then explore three potential mechanisms for core perturbation growth:
  1. Centrifugal instability due to vortex circulation overshoot,
  2. Kelvin wave growth due to resonance with the external turbulence, and
  3. Transient growth of perturbations in the normal-mode stable vortex.
We show that transient growth of bending waves can produce orders of magnitude growth in core turbulence and hence possible breakup of trailing vortices -particularly at Reynolds numbers relevant to aircraft.