Re: Chladni's Figures

[William Beaty <billb@ESKIMO.COM>]

On Sun, 28 Oct 2001, brian whatcott wrote:

> I read about Chladni's figures (1787) when I was a kid.
> A glass square is supported from the center on a stand,
> and lycopodium powder - whatever that is - is sprinkled

For anyone with time to kill, don't miss the 'Oscillons' or 'Cymatics'
demo/artform.  This is otherwise known as fluidized powder on a vibrating
table.  It's very similar to the Chladni plate, but it differs in that
the oscillon table has no nodes/antinodes.  All of the amazing patterns it
produces are based upon nonlinear interactions.  A similar
effect is sometimes seen with Chladni plates when tiny patterns arise
within a single antinode (e.g. those strange parallel walls of powder in a
Kundt's tube.)  These are also seen when sawing plywood with a sabre saw:
the sawdust on the vibrating board self-organizes into rows of tiny peaks.

To make a simple version, glue a thin plastic dish to the cone of a 12"
loudspeaker, place the speaker on a tabletop, then use an oscillator and
an amp to play a loud constant tone (earmuffs required.)  Pour a couple
tablespoons of flour or baking soda onto the vibrating dish and watch what
happens.  If you use white powder, paint the dish black for contrast.

Different patterns will spontaneously arise at different frequences and
with different types of powder (or try various liquids).  A few that I
recall:

 Arrays of tiny piles of powder which slowly crawl around on the surface.

 Interdigitated moving rows which resemble the BZ reaction-diffusion demo

 "Volcano" cones where powder pours out of the peak, flows down the
 sides, then crawls underneath the pile to repeat the cycle.  Larger
 "volcanos" even spew a spray of powder from their peaks.

 "Galaxies", rotating 2-armed spirals with a clot of powder in the center.

 "Slugs", oblong piles which move around as if alive, while complicated
 waves writhe upon their surfaces.


Here are some links with photos of nonlinear vibrating powders:

http://www.biosonicenterprises.com/products/greenimage.gif
http://www.biosonicenterprises.com/products/blueimage.gif
http://www.aip.org/physnews/graphics/html/oscillon.htm
http://www.aip.org/physnews/graphics/html/oscillons.html
http://www.dromo.com/fusionanomaly/hansjenny.jpg
http://chaos.ph.utexas.edu/research/granular/sandpic.html
http://www.mysticalsun.com/cymatics/cymatics6.gif
http://www.utexas.edu/cons/admin/publications/focus/sum98/cnld.html
http://www.cmu.edu/adm/uri/prwebsite/bramel.html

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William J. Beaty                                  SCIENCE HOBBYIST website
billb@eskimo.com                                  http://www.amasci.com
EE/programmer/sci-exhibits          science projects, tesla, weird science
Seattle, WA   206-789-0775          freenrg-L taoshum-L vortex-L webhead-L