A smoke ring is a visible vortex ring formed by smoke in a clear atmosphere.
Smokers may blow smoke rings from the mouth, intentionally or accidentally. Smoke rings may also be formed by sudden bursts of fire (such as lighting and immediately putting out a cigarette lighter), by shaking a smoke source (such as an incense stick) up and down, by firing certain types of artillery, or by the use of special devices, such as vortex ring toys. The head of a mushroom cloud is a large smoke ring.
A smoke ring is commonly formed when a puff of smoke is suddenly injected into clear air, especially through a narrow opening. The outer parts of the puff are slowed down by the still air (or by edges of the opening) relative to the central part, imparting it the characteristic poloidal flow pattern.
The smoke makes the ring visible, but does not significantly affect the flow. The same phenomenon occurs with any fluid, creating vortex rings which are invisible but otherwise entirely similar to smoke rings.
When blown in still air, a smoke ring usually travels roughly straight from the opening over a surprisingly large distance, maintaining its shape, until dispersed by turbulence or other interference.
Read more about Smoke Ring: Smoking and Breathing, Volcanoes
Famous quotes containing the words smoke and/or ring:
“God loafs around heaven,
without a shape
but He would like to smoke His cigar
or bite His fingernails
and so forth.”
—Anne Sexton (1928–1974)
“But whatever happens, wherever the scene is laid, somebody, somewhere, will quietly set out—somebody has already set out, somebody still rather far away is buying a ticket, is boarding a bus, a ship, a plane, has landed, is walking toward a million photographers, and presently he will ring at my door—a bigger, more respectable, more competent Gradus.”
—Vladimir Nabokov (1899–1977)