Undulating Skin Results In 50% Less Drag

If this technique can be adapted to gliders and other aircraft,
imagine the enabling effect it will produce:



http://technology.newscientist.com/c...-and-subs.html
Shape-shifting skin to reduce drag on planes and subs

* 13:30 16 April 2008
* NewScientist.com news service
* Colin Barras

Engineers have shown skin able to tune its wrinkles could cut
dramatically cut drag on submarines or planes (Image: IOP)
Engineers have shown skin able to tune its wrinkles could cut
dramatically cut drag on submarines or planes (Image: IOP)

Aircraft or submarines covered with an undulating skin able to
change at a flick of a button would experience 50% less drag than
conventional vehicles. This trick, which naturally occurs in
dolphins, is now being tested by human engineers.

Turbulence is the bane of engineers' lives. Chaotic air flow sets
up unstable vortices and patterns in gases and liquids, increasing
friction and drag.

Giving craft skin than can tweak its surface to impose order on
these currents could dramatically cut the effect of drag, says
Dimitris Lagoudas at Texas A&M University, US. Calming the chaotic
waves makes them interact less with the skin. "The particles in
the fluid stop "speaking" to the craft’s surface," he says.

Lagoudas and colleagues have worked out that wrinkling the surface
of a craft in the right way can cut problems. The surface must
assume the shape of the ideal ordered surface wave it is trying to
create, something that changes at different velocities.

Dolphin trick

It might seem counterintuitive to reduce drag by wrinkling the
surface of a craft, but nature provides a precedent. "Dolphins
induce their skin to wrinkle, so water won’t stick to them," says
Lagoudas.

After calculating that this approach would work, his team tested
designs for an "active skin" that shifts to ...

More...
http://technology.newscientist.com/c...-and-subs.html