I was really just kidding about Great White, I'm sure you've more sense than that (should've added a smily).

One further thought - you could use a standard plumber's butane torch as your igition source - very hard to blow out, with a good long directional flame. I'd imagine a canister of fuel would last 30-40 minutes if set low enough.

Essentially, you want to make a large bunson burner, it seems. A large tube set vertically fed from the bottom with gas, a relatively large diameter and an adjustable air inlet (so you could tune the gas/air mixture, and some length to make sure the gas and air mix, hitting an open flame just past the top of the open tube. By adjusting your gas flow and air mixture you should be able to make anything from a wavy flame to a jet type flame. You could place your gas valve well away from this and turn it on and off by hand (stage hand's job).

This of course assumes you're using a lighter-than-air gas, it would be disasterous to use a fuel whose vapors sank.
-Zeke