In the not distant future you may notice two remarkable things
about a landing airplane: The landing gear glow purple and the
landing is much quieter than you'd expect. The two linked curiosities
result from some innovative technology developed at Notre Dame.
For some time, engineers have known they could make an airplane
touchdown less noisy by streamlining the landing gear. Manufacturers,
however, haven't incorporated the designs because mechanical wind
screens add weight, don't stow easily and are difficult to maintain.
Now, however, Flint O. Thomas and Thomas Corke, Notre Dame professors
of aerospace and mechanical engineering, have come up with a novel,
nonmechanical way to streamline landing gear by ionizing the air
around the apparatus. The concept is elegant: Strategically placed
electrodes linked by a dielectric material, which supports electrostatic
fields, produce a glowing purple plasma of ionized air that sucks
surrounding air down, channeling it near the surface. Since noise
is created when air flow separates from a surface, the streamlining
effect of the plasma significantly reduces airplane noise by keeping
the flow close to the landing gear.
In wind tunnel tests at Notre Dame, Thomas and Corke have demonstrated
that just two plasma actuators reduced aerodynamic drag by 90
percent and significantly suppress noise. "With refinements we're
confident we can do even better than that," Thomas says.
The plasma streamliners have several advantages, the Notre Dame
researcher says: They don't require a great deal of power, can
be turned on as needed, are relatively inexpensive and can easily
be retrofitted to existing aircraft. The commercial airplane industry
is keenly interested in the technology.
(October 2005)
