Whale Flippers Make Better Airplane Wings

phreakmonkey writes "The bumpy, ridged surface on humpback whale flippers provide more lift, less drag, and exhibit better stall characteristics than traditional aircraft wing designs, according to Duke University, West Chester University, and the U.S. Naval Academy. This could help improve the design of airfoils used on everything from aircraft wings to underwater vehicles. The results were published in the May 2004 issue of Physics of Fluids and reported on Innovations Report."

Comments

Golf Ball Dimples

[joelparker]

Bumps and dimples tend to make things fly more reliably, by letting small eddies of air whirl. The same effect can be seen in golf balls-- a golf ball with dimples (like all the ones today) will fly farther and straighter than a perfectly spherical one.

Why does a golf ball have dimples?

Re:bumps

[MoeDrippins]

There have been a number of things where bumps (or otherwise non-flat/smooth) surfaces have helped aerodynamics; golf-ball dimples being the most recongizable example. If I recall correctly, some of the speed-skaters in the Olympics a few years back were wearing some whiz-bang body suit that had some "deformations" under the arms or somesuch for the same reason.

Here's one mention of something related.

Re:Bumps are vortex generators

[phreakmonkey]

Actually, I disagree. The increased low-speed handling (and higher angle of attack) characteristics of wings with vortex generators have been known for a long time. However, traditionally shaped vortex generators tend to increase drag, or at best leave it the same.

What appears to make this shape unique is that it actually increases the lift of the wing, increases the range of angle of attack (= lower stall speeds) AND reduces drag. This means it's more aerodynamically efficent overall, instead of trading one aerodynamic characteristic for another. (ie: increasing drag to lower the stall speed)

We haven't improved the overall efficency of wing design for some time. (That's why a 1967 Cessna 172 and a 2003 Cessna 172 have nearly identical wings.) This may change that.

- pm

Re:bumps

[Weh]

the strips on those suits are basically designed to 'trip' the flow so that it becomes turbulent (instead of laminar). Turbulent flow has more momentum which results in less pressure drag. The disadvantage of turbulent flow over laminar flow is that it gives more viscous drag.

Dimples in a golf ball are designed to increase the roughness so the amount of air being held to the surface of the ball is greater when the ball rotates. Higher air velocity (at the top) and lower velocity (at the bottom) create a pressure difference which gives lift.