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Birds Give a Lesson to Plane Designers
Roland Piquepaille points out a news release from the University of Michigan where researchers are looking to birds and bats for insights into aerospace engineering. Wei Shyy and his colleagues are learning from solutions developed by nature and applying them to the technology of flight. A presentation on this topic was also given at the 2005 TED conference. From the news release:
"The roll rate of the aerobatic A-4 Skyhawk plane is about 720 degrees per second. The roll rate of a barn swallow exceeds 5,000 degrees per second. Select military aircraft can withstand gravitational forces of 8-10 G. Many birds routinely experience positive G-forces greater than 10 G and up to 14 G. Flapping flight is inherently unsteady, but that's why it works so well. Birds, bats and insects fly in a messy environment full of gusts traveling at speeds similar to their own. Yet they can react almost instantaneously and adapt with their flexible wings."
Current aircraft performance is limited by what the occupants can survive. Try to roll a human at 5,000 degrees per second and things would get messy.
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a barn swallow, yes, but an African swallow...
I can't remember the source, but several years ago, a researcher in his twenties saw how owls' wingtips point upward on their downstroke. This cuts down on vorticies at the wingtips, making for a more efficient and quiet flight.
Airplane designers then took that idea and applied it to most commercial jets you see today.
This is really amusing, but least I laugh to hard allow me to enlighten some...
The mighty Peregrine Falcon, THE fastest animal in the skies, bar none, have been clocked in dives exceeding 200mph, with radar. Now that is pretty damn fast for anything made of bone, muscle and sinew and covered in something as delicate as feathers. But one has to examine the actions of the animal when it accomplishes these seemingly impossible feats of speed.
Fist of all, much like the famous ( or infamous depending on your POV, especially if you were a pilot in the early very underpowered versions ) F-14 Tomcat Naval Jet Fighter, it makes maximum use of variable wing geometry. When a Peregrine stoops ( the technical term for diving from altitude in the bird world ) its 39 to 43 inch wings fold in very tightly making the outline of the bird look pretty like a "W", leaving just enough airfoil hanging out to effect control. This reduces stress on the main wing spar ( their bones and joints ) by a huge margin thus allowing it to accomplish this feat without tearing its wings off.
Now I don't have an actual measurement of their wing span in a full speed stoop, but from photo's I estimate that it reduces wing span by a good 75% or more. The area of the wing that would comprise the distance between a human elbow and the tips of our fingers goes parallel to the body and the upper wing ( the area from a human shoulder to the elbow ) then are pulled in close to the head, further reducing wing span.
Transition from this "clean" configuration to a "Dirty" configuration after either missing or hitting its prey can be quite rapid and causes the bird to bleed off speed at a very high rate. A Falcon cannot make a "pylon" ( a turn in an airplane in which one rolls the airplane from straight and level flight by nearly 90 degrees and then applies maximum UP elevator ) turn, the force on the wings would quickly overcome the bone, tendon, muscle and joint strength. Now this is not to say the are not maneuverable in a stoop but as you would surmise their maneuverability is greatly reduced at speed. Another very interesting feature of the bird is its nostrils. Small bony tubercles in a falcon's nostrils guide the air and shock wave to prevent over pressuring the lungs and giving the bird the ability to breath while diving.
so while looking to nature can be inspiring for aeronautical design there are very real limitations in duplicating the ability of a bird with mechanical devices. Another instance would be the original Wright Flyer. It did not have ailerons, it used what is called "Wing warping" which is what birds do, but it was found to be quite impractical since the amount of wing warping required to provide the same effectiveness as a bird required that the wings be so flexible to the point of losing to much strength. Now birds do Wing warping one better as they can not only warp their wings but they can dip a wing, decrease span, warp, move their tail in all axes, and do this all at the same time, providing maneuverability that airplane designers can only dream of.
On whales and submarines. If it were not for the requirement that we a) Keep the water out of the people tank and b) be able to stay submerged for months on end, and c) carry weapons that are stand-off capable, perhaps a Blue Whale would be a decent model to study in submarine development, but not as much as one would think. One must remember that a whale of any kind is a completely articulated bit of construction. It can bend and twist in any direction thus altering its hydrodynamic profile at will. Careful study of its means of propulsion reveals that it is a "whole body" movement, not simply a movement of the flukes in an up and down motion. It was also discovered some time ago that whales overcome friction in the water by way of their blubber. Careful examination revealed that hydrodynamic pressure is relieved by the blubber and skin actualy undulating in concert with the pressure waves to facilitate their movement dow
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