On Sat, Mar 28, 2009 at 01:24:22PM -0700, Kyle Mcallister wrote: >... >A pulse of air, it seemed, was jetted from the hole, >once per spark, and could be felt physically impacting >against my skin at almost 2 feet away. It was in a >very thin beam. It did not pass through metal or >plastic, but would make them vibrate with the impulse. >Thinking that this was just air overpressure, I moved >the spark plate apparatus a bit farther away. The idea >was, if it was overpressure from the spark shooting >out an air vortex (like a smoke doughnut... YES! LET'S >CALL THESE AIR BISCUITS!),
How about going back to this more successful first configuration, with the small hole in the steel plate, filling the spark tube with smoke, and then turning on the -100KV? Hopefully the sphere can charge up and start sparking before the smoke in the tube dissipates. Or maybe rig a yard-long piece of flexible plastic tubing to the spark tube that you can blow smoke into the other end of, using a remote-controlled pump (since a spark could conceivably travel down the smoke in the tubing). Maybe you'd see a smoke-ring or some other soliton-type body of smoke shoot out of the tube when the spark fired. You can make a smoke-ring type air pulse generator using a cylindrical tube with a rubber membrane covering one end. Thump the membrane (or pull on the center and then let go) and it shoots a toroidal soliton of air that you can feel across a room. (Wonder how a cat would react to it? >8^) There's a commercial toy like this, but I don't remember the length:width ratio, which may be critical. I vaguely recall it being about 2:1. Maybe a Morton salt box would work, but I think the toy I saw was 2 or 3 times that size. Maybe the spark is simply causing a temperature jump in the air inside the tube, causing it to expand suddenly and shoot a small vortex ring, as you suspect. (Is a smoke-ring properly called a "vortex"?) That would explain why the hoped-for "force beam" can't go through metal or plastic. Another approach to visualize an air pulse would be a wide-angle schlieren system with a high-speed video camera. Maybe at a local university? If the air is warm it might refract light enough to show up. http://en.wikipedia.org/wiki/Schlieren Mark
