Al''s water analogy..
Archiver
Posts: 46,084
I am NEVER giving a smart-*** answer again !!!
Chris
Original Message
From: Tracy Allen <tracy@e...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, May 04, 2001 3:22 AM
Subject: [noparse][[/noparse]basicstamps] Re: Al's water analogy..
> > >If I punch a hole the size of my fist in the tank, more
> > >water will flow per second, but it won't be under so much pressure
> >
> >Initially the pressure will be the same for both holes, as they would
> >presumably be at the same depth from the surface of the water, the
pressure
> >will reduce faster for the larger hole.
>
> Unless, of course, the tank is set up as a magically simple mariotte
> siphon, then the pressure at the bottom is constant (down to a
> point)! It is a fluidic "voltage regulator".
> http://www.uswcl.ars.ag.gov/exper/mariotte.htm
>
>
> >Consider that your water pressure literally comes
> >from a big tank of water now (that's why water towers are -- well --
towers
> >unless you live somewhere where they build them on a mountain or other
> >elevated area). When you use your garden hose, water comes out and that's
> >purely from the pressure of your city's water tower. If you occlude part
of
> >the hose orifice, the pressure goes up dramatically.
>
> Unless you are standing right under the tank, there is considerable
> "source resistance" in the pipe that leads from the water tower to
> your house. It is analogous to a voltage divider. If your hose is
> set for a small orifice, low flow, it is backed up by the full
> available pressure. There is not much pressure drop in the piping up
> to your house. Large orifice, high flow, the pressure drops across
> that source resistance.
>
> To put it another way: The closed faucet may be backed up by 85psi,
> and that is as high as it gets, effectively the pressure in the city
> system. As you try to get more volume flow, the pressure at your
> faucet drops. When the faucet is full open, the flow rate is equal
> to that 85psi divided by the total resistance of the plumbing from
> the city's tank up to your faucet. And when all your neighbors are
> irrigating their cabbages, your pressure drops too, because it is all
> one big network of resistances, flows and pressures.
>
> ---
>
> At school one time we were thinking about what would be a good
> fluidic analogy for an inductor. Imagine that water in a pipe has to
> flow through a closed paddlewheel arrangement, and the paddlewheel
> turns a heavy flywheel. Then when you put pressure across it, the
> flow has to build up slowly as the flywheel gains momentum. And the
> flywheel can keep the flow going. If you try to stop the flow
> suddenly, you get a big kick in pressure as the flywheel tries to
> conserve momentum.
>
> >Sometimes water analogies can turn to rubbish, but like you said, if it
gets
> >some work done....
>
> ...it's fun, it's tangible....
>
> -- Tracy
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>
Chris
Original Message
From: Tracy Allen <tracy@e...>
To: <basicstamps@yahoogroups.com>
Sent: Friday, May 04, 2001 3:22 AM
Subject: [noparse][[/noparse]basicstamps] Re: Al's water analogy..
> > >If I punch a hole the size of my fist in the tank, more
> > >water will flow per second, but it won't be under so much pressure
> >
> >Initially the pressure will be the same for both holes, as they would
> >presumably be at the same depth from the surface of the water, the
pressure
> >will reduce faster for the larger hole.
>
> Unless, of course, the tank is set up as a magically simple mariotte
> siphon, then the pressure at the bottom is constant (down to a
> point)! It is a fluidic "voltage regulator".
> http://www.uswcl.ars.ag.gov/exper/mariotte.htm
>
>
> >Consider that your water pressure literally comes
> >from a big tank of water now (that's why water towers are -- well --
towers
> >unless you live somewhere where they build them on a mountain or other
> >elevated area). When you use your garden hose, water comes out and that's
> >purely from the pressure of your city's water tower. If you occlude part
of
> >the hose orifice, the pressure goes up dramatically.
>
> Unless you are standing right under the tank, there is considerable
> "source resistance" in the pipe that leads from the water tower to
> your house. It is analogous to a voltage divider. If your hose is
> set for a small orifice, low flow, it is backed up by the full
> available pressure. There is not much pressure drop in the piping up
> to your house. Large orifice, high flow, the pressure drops across
> that source resistance.
>
> To put it another way: The closed faucet may be backed up by 85psi,
> and that is as high as it gets, effectively the pressure in the city
> system. As you try to get more volume flow, the pressure at your
> faucet drops. When the faucet is full open, the flow rate is equal
> to that 85psi divided by the total resistance of the plumbing from
> the city's tank up to your faucet. And when all your neighbors are
> irrigating their cabbages, your pressure drops too, because it is all
> one big network of resistances, flows and pressures.
>
> ---
>
> At school one time we were thinking about what would be a good
> fluidic analogy for an inductor. Imagine that water in a pipe has to
> flow through a closed paddlewheel arrangement, and the paddlewheel
> turns a heavy flywheel. Then when you put pressure across it, the
> flow has to build up slowly as the flywheel gains momentum. And the
> flywheel can keep the flow going. If you try to stop the flow
> suddenly, you get a big kick in pressure as the flywheel tries to
> conserve momentum.
>
> >Sometimes water analogies can turn to rubbish, but like you said, if it
gets
> >some work done....
>
> ...it's fun, it's tangible....
>
> -- Tracy
>
>
>
>
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
>
>