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

What conditions does this effect need?

[Retric]

The tests show that bump-ridged flippers do not stall as quickly and produce more lift and less drag than comparably sized sleek flippers.
...
The row of tubercles sheers the flow of water and redirects it into the scalloped valley between each tubercle, causing swirling vortices that roll up and over the flipper to actually enhance lift properties.

This sounds like the same effect that Honeybee's use, but I can't help but wonder what range of wind speeds this works for. My guess would be this is only useful for subsonic aircraft. Even if the effect were limited to say 1/2 the speed of sound there are plenty of aircraft that could benefit from this. If anyone can find a link which gives the conditions required for this effect that would be great until then I am going to assume it's not gong to work on a 747. Although some cessnas's might end up with bumpy wings.

Learning from nature

[Gallowsgod]

I think science could do well learning more from nature. After all, nature have perfected lots of designs over millions of years.

Take bats for instance, only after spending years inventing sonars and radars we humans discover these little creatures had used the same solutions for quite some time.

Ricard Dawkins' brilliant book The blind watchmaker did a good job convincing me that we still have lots and lots to learn from nature.

Re:bumps

[M1FCJ]

Lift generated by a rotating body vs. lift generated by a rotating body generating turbulance. Interestingly enough turbulence helps. In high speeds laminar flows are not that good, in many aircraft sharp edges and slits on the wing are used to generate turbulance so that the shock wave won't be happening on the wing surface itself. It is not very good for lift. (When the aircraft is flying around 0.9M, the air flowing over the wing can move faster than sound).

TRIZ predicts this

[wjwlsn]

TRIZ is a step-by-step method for generating innovative solutions. That sounds stupid, I know, but bear with me. TRIZ is based on resolving contradictions between parameters... in classical TRIZ, there are 39 such parameters, mostly engineering focused. You have a contradiction when you have 2 parameters in conflict, where improving one of them makes the other worse. Your ideal solution would have BOTH improve.

Considering air flowing over an airfoil, I can see contradictions between lift (pressure, parameter 11) with speed (parameter 9) and energy spent (parameter 19). TRIZ then suggests inventive principles that might present a solution. Some promising hits appear to be:

• Spheroidality - Replace flat parts with curved ones. (principle 14)
• Vibration - Set an object into oscillation, or if oscillation exists, increase its frequency. (principle 18)

There are plenty of other ways to look at this, and possibly other principles might come into play. Combinations of principles might work as well... this seems to be the case with the principles found above.

For more info, check out the following site - TRIZ.

Please note that I have no connection with this site.