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Author Topic: Does waste reach terminal velocity on its way down to the sewers?  (Read 6393 times)

Jonathan Shapiro

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Jonathan Shapiro asked the Naked Scientists:
Sorry about this.

If you flush a No.2 from a loo on the 98th floor of a tower office block, does the missile-shaped deposit plummet straight down and smash into the bottom of the drain,leaving an incredible skid mark, or does it gently land to be wafted away by the water?
What do you think?


 

Offline ukmicky

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I doubt the poo's journey is straight down so no probably not.
 

another_someone

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What is terminal velocity in this case?  Is not terminal velocity contextual, being that velocity where the frictional forces balance the gravitational forces, and so in this case, is it not merely that the frictional forces being greater, mean that terminal velocity is very much lower, and that lower terminal velocity is indeed reached?
 

Offline turnipsock

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When you stay in a hotel, why is there always somebody on the top floor that insists on flushing the toilet in the middle of the night? Is it the same person?

 

Offline JimBob

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Most probably not. In order for to real terminal velocity in a pipe the fluid, or fluid mixture in this case, must be in a state called laminar flow. That means there is no turbulence. No sewer pipe with a no 2 is going to have laminar flow. It will be turbulent flow.

For the definitions of laminar and turbulent flow see:

http://en.wikipedia.org/wiki/Laminar_flow  - the picture of smoke on this page shows both laminar and turbulent flow.
 

Offline neilep

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Jonathan Shapiro asked the Naked Scientists:
Sorry about this.

If you flush a No.2 from a loo on the 98th floor of a tower office block, does the missile-shaped deposit plummet straight down and smash into the bottom of the drain,leaving an incredible skid mark, or does it gently land to be wafted away by the water?
What do you think?




I luff the idea of my poo travelling at a 120 mph !!

Please let it be yes !!
 

Offline chris

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It will be turbulent flow.

turbulent?

"turdulent" more like.
 

lyner

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Even if it's going down a slope it will still reach 'A' terminal velocity i.e. it won't go any faster.
It's bound to touch the sides of a 'vertical run', in any case, so it won't end up very fast.
« Last Edit: 02/05/2008 13:12:54 by sophiecentaur »
 

Offline JimBob

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Even if it's going down a slope it will still reach 'A' terminal velocity i.e. it won't go any faster.
It's bound to touch the sides of a 'vertical run', in any case, so it won't end up very fast.

I was considering terminal velocity as the maximum velocity gravity could produce, not th maximum velocity that flow through a pipe would produce.

It doesn't make any difference - it is still a dirty business.
 

Offline science_guy

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It will be turbulent flow.

turbulent?

"turdulent" more like.

 [xx(] :o :D :D

that just about sums it up
 

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