Dolphins Blowing Rings

>> Humans blow smoke rings but dolphins have a much healthier habit. >> The attached video is of dolphins playing with rings which they have >> the ability to make under water to play with. It isn’t known how they >> learn this, or if it’s an inbred ability. >> >> As if by magic the dolphin does a quick flip of its head and a silver >> ring appears in front of its pointed beak. The ring is a solid, donut >> shaped bubble about 2-ft across, yet it doesn’t rise to the surface >> of the water! It stands upright in the water like a magic doorway to >> an unseen dimension. >> >> The dolphin then pulls a small silver donut from the larger one. >> Looking at the twisting ring for one last time a bite is taken from >> it, causing the small ring to collapse into a thousands of tiny >> bubbles which head upward towards the water’s surface. After a few >> moments the dolphin creates another ring to play with. There also >> seems to be a separate mechanism for producing small rings, which a >> dolphin can accomplish by a quick flip of its head. >> >> An explanation of how dolphins make these silver rings is that they >> are”air-core vortex rings”. Invisible, spinning vortices in the water >> are generated from the tip of a dolphin’s dorsal fin when it is >> moving rapidly and turning. When dolphins break the line, the ends >> are drawn together into a closed ring. The higher velocity fluid >> around the core of the vortex is at a lower pressure than the fluid >> circulating farther away. >> Air is >> injected into the rings via bubbles released from the dolphin’s >> blowhole. The energy of the water vortex is enough to keep the >> bubbles from rising for a reasonably few seconds of play time.