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On Tue, 18 Mar 1997, Leigh Palmer wrote:
about aGreetings everyone! I saw an advertisement a while ago
over asinging pipe. You place a pipe that has a wire mesh inside of it
letsbunsen burner. When you remove the pipe from its heat source, it
off a tone/moan.
I found this ancient while cleaning out old mail in my inbox.
If anyone here can quickly set up a Rijke Tube demo, I have something
for
you to try out. The Singing Pipe normally goes silent when turned
horizontally. Two theories popped up after some debate on the SAS
forum:
the sound being driven by sudden density changes and gravity, versus
the
sound being generated by a sort of Stirling Engine effect, with the
air
acting as the engine's piston, and the resonant mass acting as the
flywheel.
To further investigate this, I'd like to find out if the Rijke Tube
still
makes noise if positioned horizontally while being provided with a
gentle
air flow from a nearby fan. If the effect comes from gravity, then it
will always fail when the tube is horizontal, even if the "convection"
wind is supplied with a fan. If the effect is driven by a heat
engine,
then the "howl" will appear as long as there is slow wind through the
tube, even if the tube is horizontal.
These are called "Rijke tubes". The gauze is optimally placed onequarter
of the length from the bottom of the tube. The ones I've made arealso of
50 mm diameter glass, with about 3 mm spaced brass wire gauze. I'vemade
quite a few of these and have kept a set which is tuned to a majortriad
plus the octave. They are deafening!had a
I cannot explain simply (or otherwise) how these tubes work. Brian
Pippard (former Cavendish Professor of Physics at Cambridge) and I
go at trying to understand them during his visit to Simon Fraserthirty
years ago. After he left we continued a correspondence about them,and
he believed that he did understand them, but I was incapable ofquite a
understanding his explanation, which was nonmathematical. I saw
bit of Brian during my stay in Cambridge a couple of years ago, butI
didn't renew the discussion. Brian told me that schoolboys inBritain
had made drainpipes sing by shoving lighted newspapers up into themfrom
below. I was unable to duplicate the feat, even with his help. Hehad
never done it himself.convection.
What can be said confidently is that the tubes are powered by
When mine are laid over sideways they become utterly silent. Afterbeing
left that way for ten seconds or so I can turn them vertical andthey
sing loudly again, seemingly with no energy source. It is quite a
dramatic effect.
I, too, would like to know how these things work.
Leigh