Vortex ring toy
A vortex ring toy is any of several toys that generate vortex rings – rolling torus-shapes of fluid, similar in structure to smoke rings – that move through the fluid (most often air, and sometimes water).
Because of the way they rotate, a vortex ring can hold itself together and travel for quite a distance. Toys that blow air vortices, like the air vortex cannon, are mainly used to tickle people or animals at a distance with an "invisible hand". An interesting demonstration is to have a smoker blow a smoke cloud into the toy just before firing, to create a large smoke ring. Some toys have a built-in smoke generator for this purpose.
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References
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