SMOKE RINGS, PROGRAMMABLE VORTICITY, DELAYED DISRUPTION, REVERSE SPINS,  ETC.
                                                William J. Beaty, Aug 1999


See if this makes sense.  If you take your hole-bearing oatmeal box and
give it a whack, and air begins moving out through the the circular
orifice, a sort of infinitely thin ring-defect in the air is first
generated.  Then as more air moves along, the ring-defect "winds up" 
succeeding layers of air having a changing tangential velocity over time. 
Since "onion layers" are building up on the ring over time, a
vortcity-profile is being "programmed" as the smoke ring is being created. 
Finally the flow ceases and the ring-vortex attains independent life.  But
more than this can be done... 

Years ago I had suspicions that something like the above was possible,
that's why I put the suggestion on my website that kids should try using a
loudspeaker and a waveform editor as the "membrane pulse generator" of a
smoke ring launcher.  Now I see that such a device can be used to
"program" the distribution of tangential velocity in the smoke ring.  Vary
the velocity/time profile of the mechanical pulse applied to the
launcher's membrane, and you vary the distribution of tangential velocity
surrounding the core of the resulting vortex ring.  For example, if we
give the membrane a sort of "finger tap" pulse which has rapid onset and
slow decrease to zero velocity, then the resulting vortex ring travels
very slowly, but at the same time has a core which spins fiercely, and
which often becomes unstable and "shatters" the entire vortex structure
after a time delay. 

Or, we could do the opposite and send a slowly growing pulse which ends
suddenly.  The resulting vortex ring will have all its tangential velocity
concentrated on its "outer skin", and as a result the air within the
"donut" will barely spin at all, while the vortex as a whole will go
racing forwards like some sort of bullet.

Maybe its even possible to create a ring-vortex entity which races
forwards, but whose core spins backwards!  (Blasphemy!)  Simply start out
by briefly "sucking" before reversing the membrane travel and creating a
normal vortex.  Or will this tend to "unwind" the vortex core rather than
applying some high shear and creating a backwards tangential flow to the
outer layers of the growing ring-vortex structure? 

Is this phenomenon well known?  Or might some aspect of it be worthy of
publication somewhere?  (When I myself ever get off my butt and build a
"computer synthesized vortex launcher" I might at least get the plans
published in AJP, etc., as a suggested educational device.) 

Gotta make smoke rings which "explode" after a programmable time delay, or
smoke rings where the core spins backwards... 


((((((((((((((((((((( ( (  (   (    (O)    )   )  ) ) )))))))))))))))))))))
William J. Beaty                                  SCIENCE HOBBYIST website
billbeskimo.com                                  http://amasci.com
EE/programmer/sci-exhibits          science projects, tesla, weird science
Seattle, WA   206-762-3818          freenrg-L taoshum-L vortex-L webhead-L