8 Percent More Lift and 32 Percent Less Drag

Just when you thought aviation science had reached it limit:



http://www.aopa.org/members/files/pi.../news0508.html
Dept. of R&D
A whale of a tale
To improve aircraft wing design, scientists have turned to one of the
most unlikely sources in natu humpback whales.

Wind-tunnel tests using scale models of humpback pectoral flippers
have shown that the bumpy flipper is a more efficient design and has
better stall characteristics than anything currently in aviation. The
results were previously reported by researchers from West Chester
University, Duke University, and the U.S. Naval Academy in the journal
Physics of Fluids.

The researchers compared a smooth flipper, similar to a modern
airplane wing, with one that had bumps or what are called tubercles.
The bumpy flipper produced 8 percent more lift and 32 percent less
drag, and stalled at a 40 percent steeper angle. The researchers said
that as a whale moves through water, the tubercles cause swirling
vortices by disrupting the line of pressure against the leading edge
of the flippers. The water is redirected into the scalloped valleys
between the tubercles, keeping the flow attached to the upper surface
of the flipper.

The findings could be applied not only to airplane wings, but also to
the tips of helicopter rotors, airplane propellers, and ship rudders.