1. Hey guys,
i've got a question, this year on school i have my final project, i decided to make a vortex cannon,
but for that i would like to know a formula, if i have a cylinder, or a conus, what would need to be
the diameter for the hole in front of the cylinder, so that it will schoot a vortex?

thanks anyway

2. A vortex of what?

3. I'm not sure Barry. I've seen pictures and videos of what is essentially a puffer-box that blows a smoke-ring vortex, but I don't know the dimensions of it. Maybe there's something in here: http://www.maths.ed.ac.uk/~aar/papers/silliman.pdf. Here's an excerpt:

"On a day in mid-January, 1867, Peter Guthrie Tait set up some homely apparatus in his lecture room at Edinburgh and proceeded to create a " magnificent display" of smoke rings. Expelled from two boxes situated at varying angles from one another, the smoke rings behaved in a most curious manner. When two rings were made to travel in the same direction with their centers in the same line and their planes perpendicular to this line, the leading ring expanded and moved more slowly; the pursuing ring contracted and moved faster; and each in turn passed through the other. When, however, two rings were made to approach each other from opposite directions, both of them expanded and moved more and more slowly, never quite touching. Propelled toward each other at oblique angles, the rings glanced off each other without coming into actual contact and thereafter went into a state of violent vibration. No less remarkable was the fact that individual smoke rings resisted all efforts to cut them with a knife. No matter how vigorous the slicing motions, the rings simply moved away from, or wriggled around, the sharp instrument."