Author Topic: Von Karman Vortex Street  (Read 1330 times)

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Offline mayya

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Von Karman Vortex Street
« on: September 18, 2013, 00:01:40 AM »



Von Karman Vortex Street


http://i.livescience.com/images/i/000/049/118/i235/von-karman-vortex-street-11120902.jpg
Credit: Von Karman Vortex Street: Bob Cahalan, NASA GSFC

In the field of fluid mechanics, physicists look at the flow of fluids through space and the patterns they make. One of the more beautiful patterns they study are the swirling set of eddies and whirlpools that things like boats leave behind in their wake. As the boat moves through the water, it slices the fluid in half. As the water reunites behind the boat, it creates a pattern of alternating vortices known as the Von Karman vortex street.

The phenomenon is important to all kinds of questions. Tall buildings, chimneys and submarine periscopes, for example, all have to deal with the wind that whips around them. As the wind comes around and then circles back, the force can cause those structures to vibrate forcefully. Some structures, such as antennas and periscopes, have fins to cut the wind and prevent the eddies on either side from meeting.

And it's not just big things that have to deal with the vortex street. As insects beat their wings, they create tiny vortices in the air. But rather than accepting the drag that a vortex can create, the insects turn their wings just a little before their up stroke, so that their wings lift upward along with that swirling current of air.


http://www.livescience.com/33628-funny-physics-theorems-names.html