Yeah. You should blow air up the stack. At the top of the stack, place "flame shaped" bits of colored celluloid. Place a light bulb under the strips. Make darn sure the light bulb can't start a fire.
The air will cause the strips to flutter.
You might also replace the bulb with several LED's that are flashed randomly.
Ed
I am putting together an oil refinery and would like to model the flame that shoots out of a flare stack. Any suggestions on how to model this?
Thanks In Advance
Ira