Vortex Rings

A vortex ring (or toroidal vortex), is a donut-shaped region of circulation that moves through the fluid medium. A vortex ring tends to move in the direction perpendicular to the plane of the ring, possibly extending out a considerable distance. The movement of the fluid can be classified as poloidal (related to the short route around a torus), across the circular axis of the donut, in such a way that the inner part of the ring moves faster toward the front side.

Vortex rings are produced by dolphins, humpback and beluga whales, volcanoes, atomic/hydrogen bombs, fire eaters, and obviously, by smokers. Vortex rings were first analyzed mathematically by H. von Helmholtz in 1858 [1].