[ExI] underwater sprinkler, was: RE: Musical instruments in space

[spike]

-----Original Message-----
From: extropy-chat-bounces at lists.extropy.org
[mailto:extropy-chat-bounces at lists.extropy.org] On Behalf Of BillK
Sent: Sunday, March 31, 2013 3:37 PM
To: ExI chat list
Subject: Re: [ExI] underwater sprinkler, was: RE: Musical instruments in
space

On Sun, Mar 31, 2013 at 11:05 PM, spike wrote:
>>... Ja.  But give us equations, me lad.  We cannot solve sentences and 
> paragraphs, we cannot derive a control system from it.  If we do this 
> right, we could play a song with that underwater sprinkler.  It would 
> be a fun accomplishment.  We could show it to the controls grad 
> students and ask them: can you do this?
>
>

>...I doubt it. The effect is very small...

The physics grad student would take this as a red-cape challenge.  {8-]

>... and experiments only show the effect with very low-friction bearings on
the sprinkler. i.e. a specially made sprinkler with 'expensive' bearings...

Hmmm, the way I did it uses no bearings.  I suspended the S-shaped sprinkler
by a latex tube and drew the water up thru that.  The whole experimental
setup is cheap and entertaining.  You don't even need a pump.  You can use
an aquarium or just a big bucket of water, then bring the other end of the
latex hose and put it in a gallon container of water, and evacuate the air
to get a siphon effect.  Then you lower the gallon container, water flows
backward into the sprinkler and into the gallon.  Raise the gallon and water
flows by gravity back out of the sprinkler.  You could put together
something like that with stuff you have around the house with practically no
cost at all, and it will react to extraordinarily low torques.  You could
even estimate flow rates with that simple setup.

>...But the equations are in the referenced papers.
See: <http://arxiv.org/pdf/0908.3190v4.pdf>

>...BillK
_______________________________________________

Ja, I imagine there is a non-steady state set of equations in the Jenkins
paper, ref 14.  Isn't it astonishing that all this ink has been spilled
about such an apparently trivial topic dating back from the 1880s all the
way up until at least 2009?  That blows my mind.  Even more so when I read
some of the online comments and see that this simple experiment is still not
fully understood, even by guys like me, who wasted a lot of mental clock
cycles on it and even built an experimental setup.

spike