Air rings! I saw a beluga blowing one at the Vancouver Aquarium last year, only she did it out of her mouth rather than the blowhole as seen here.
One of my rainy-day projects is to figure out the dynamics. You can see how fast the bubbles rise when the ring is broken, but all that air is happily drifting around for tens of seconds while the ring is intact. What's balancing the buoyancy force?
Err... was I supposed to be paying attention to the critters?
Don't think of it as an air ring. Think of it as a water ring with air trapped in it. The volume of water making up the vortex is much larger than the air volume.
(The dynamics are the same as a smoke ring. I was once watching fireworks on a roof and an eight-foot smoke ring drifted down from the range, ring over our heads.)
In principle I see how it works--thinking about an individual air bubble being dragged around by the water vortex ring makes that clear--it just amazes me that the actual ratio of forces involved is such that these rings can be so large and stable for such long times. I wouldn't have thought the viscous boundary layer at the air-water interface was up to the job, although it obviously doesn't much care what I think!
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A cute kitty video
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One of my rainy-day projects is to figure out the dynamics. You can see how fast the bubbles rise when the ring is broken, but all that air is happily drifting around for tens of seconds while the ring is intact. What's balancing the buoyancy force?
Err... was I supposed to be paying attention to the critters?
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(The dynamics are the same as a smoke ring. I was once watching fireworks on a roof and an eight-foot smoke ring drifted down from the range, ring over our heads.)
no subject