After weeks of pestering, we finally give in and let George build a vortex cannon - with surprisingly spooky cup flying results. For more information on the physics behind this head on over to http://www.urn1350.net/thescienceshow to listen to the full podcast!
A vortex ring, also called a toroidal vortex, is a region of rotating fluid moving through the same or different fluid where the flow pattern takes on a toroidal (doughnut) shape. The movement of the fluid is about the poloidal or circular axis of the doughnut, in a twisting vortex motion. Examples of this phenomenon are a smoke ring or a microburst
A vortex ring toy generates vortex rings – rolling torus-shapes of fluid – that move through the fluid (most often air, and sometimes water). [...] A vortex cannon generates vortex rings, typically using acetylene-air or hydrogen–oxygen explosions.