Examples from the Web for vortex ring
Now this is just what a vortex-ring would do in an incompressible frictionless fluid.The Unseen World and Other Essays|John Fiske
A vortex-ring produced in the air behaves in the most surprising manner.
One may, without mechanical difficulties, imagine a vortex-ring destroyed.
Through a vortex-ring or tube, the fluid circulates in closed lines of flow, each one of which is laced through the tube.Lord Kelvin|Andrew Gray
This vortex-ring theory shows easily how possible it is to-day to think what once was philosophically incredible.