Photo credit: Obvious Winner
A bubble ring, or ring bubble, is an underwater vortex ring where an air bubble occupies the core of the vortex, forming a ring shape. The ring of air as well as the nearby water spins poloidally as it travels through the water, much like a flexible bracelet might spin when it is rolled on to a person’s arm. Continue reading for the video and more information.
5. How To
The faster the bubble ring spins, the more stable it becomes. Bubble rings and smoke rings are both examples of vortex rings, the physics of which is still under active study in fluid dynamics.
Devices have been invented which generate bubble vortex rings. As the bubble rises it increases in diameter and the ring becomes thinner, despite the total volume inside the bubble ring increasing as the external water pressure and the surface tension pressure decrease.
Bubble rings fragment into rings of spherical bubbles when the ring becomes thinner than a few millimetres. This happens more quickly in turbulent water, but in calm water divers can achieve an external diameter of a metre or more before the bubble fragments.
Cetaceans, such as beluga whales and dolphins, blow bubble rings. Dolphins sometimes engage in complex play behaviours, creating bubble rings on purpose, seemingly for amusement. here are two main methods of bubble ring production: rapid puffing of a burst of air into the water and allowing it to rise to the surface, forming a ring; or swimming repeatedly in a circle and then stopping to inject air into the helical vortex currents thus formed.
Some scuba divers and freedivers can create bubble rings by blowing air out of their mouth in a particular manner. Long bubble rings also can form spontaneously in turbulent water such as heavy surf.