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-   -   "Insects depend on vortices to keep them aloft" (http://www.physicsforums.com/showthread.php?t=54140)

 Gonzolo Nov25-04 11:32 AM

"Insects depend on vortices to keep them aloft"

As a kid, I remember learning that aerodynamics couldn't explain how bumblebees flew. Recently (2000), much light was shed on the subject (thread title quoted from link) :

http://www.news.cornell.edu/releases..._Wang.hrs.html

My question is : is there presently any man-made device that take advantage of vortices to generate lift, as do hovering bumblebees?

Assuming we are not there, what are the smallest flying machines and how long can they fly?

 Clausius2 Nov25-04 12:07 PM

Quote:
 Quote by Gonzolo As a kid, I remember learning that aerodynamics couldn't explain how bumblebees flew. Recently (2000), much light was shed on the subject (thread title quoted from link) : http://www.news.cornell.edu/releases..._Wang.hrs.html My question is : is there presently any man-made device that take advantage of vortices to generate lift, as do hovering bumblebees? Assuming we are not there, what are the smallest flying machines and how long can they fly?
Great link, I have looked into it and that's a great source of interesting things. I don't know the answer to any of the two questions. But the only thing I can say is that the fact demonstrates there are some flow phenomenas that depends on the spatial scales. The characteristic lenght of an insect is of the same order of magnitude of the viscous characteristic lenght. It is not so in the aerodynamics of an aircraft. As you are shortening the characteristic lenght of the body, viscous effects become progressively important, and the mechanism of lifting will be different. But you can think of the lifting process of an air molecule suspended into the air of a room. Probably his movement is completely governed by the viscosity. So that, I think there is not any lower limit.

 Gonzolo Nov25-04 01:17 PM

The animation is totally wicked. The phenomena is remeniscent of Brownian motion, in that length scale is relevant in both cases. It would be quite interesting to find similitudes and differences in both phenomena, which are from two entirely different fields of knowledge, AFAIK.

 griffin Nov28-04 06:22 PM

There is a lot of research into mimicing natural fliers. Birds, Bats, and insects. I do not know of any complete successes, but I do know that if you want more info, then search UAV's (Uncrude Air Vehicles)

 Gonzolo Nov29-04 08:57 PM

Funny, I made a google search for "Uncrude Air Vehicles" and it brought me directly to here.

 LunchBox Nov30-04 01:50 PM

The military (or more appropriately DARPA) has been putting a load of money into micro-air vehicle (MAV) research.

A lot of money has been given to the University of Maryland to develop a micro-rotary wing vehicle and synthetic jet actuator controllers.

http://www.aero.umd.edu/research/agrc.html

Enjoy...

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