RogueRose
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Sipohn flow rate
I've always been curious if there is something that governs the speed at which siphoning can occur. If a pump is used to start the process and a rate
of 30 GPM is achieved, will that rate be continued when the pump is removed (as long as the outlet is below the source)?
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blogfast25
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Quote: Originally posted by RogueRose  | | I've always been curious if there is something that governs the speed at which siphoning can occur. If a pump is used to start the process and a rate
of 30 GPM is achieved, will that rate be continued when the pump is removed (as long as the outlet is below the source)? |
You can find a more or less complete mathematical derivation of how siphons work, here:
http://www.sciencemadness.org/talk/viewthread.php?tid=65532&...
In short, once initial flow is established by a pump and you then switch off the pump, the initial rate becomes irrelevant very quickly. The flow rate
of a siphon isn't affected by the initial rate but is determined by gravity and limited by friction (viscous) resistance in the siphon's pipe itself.
So if initially a rate of 30 GPM was established by the pump, after switching off the pump, the volumetric flow rate Qv will
adjust until it is approx.:
$$Q_v \approx \frac{\pi}{4}D^2\sqrt{2gy}$$
With D the siphon pipe diameter and y the height difference between the surface of the water and the outlet of the siphon. The
formula is roughly valid for internally smooth siphons that aren't too long.
[Edited on 28-5-2016 by blogfast25]
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Eddygp
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Oh wow! In spite of knowing that there have been many topics discussed here, I would have never thought that this would have been addressed already.
there may be bugs in gfind
[ˌɛdidʒiˈpiː] IPA pronunciation for my Username |
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Magpie
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| Quote: Originally posted by blogfast25 |
$$Q_v \approx \frac{\pi}{4}D^2\sqrt{2gy}$$
With D the siphon pipe diameter and y the height difference between the surface of the water and the outlet of the siphon. The
formula is roughly valid for internally smooth siphons that aren't too long.
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I thought this equation looked familiar. It is Toricelli's law, equally valid for a tank draining through an orifice:
The single most important condition for a successful synthesis is good mixing - Nicodem
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blogfast25
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| Quote: Originally posted by Magpie | | Quote: Originally posted by blogfast25 |
$$Q_v \approx \frac{\pi}{4}D^2\sqrt{2gy}$$
With D the siphon pipe diameter and y the height difference between the surface of the water and the outlet of the siphon. The
formula is roughly valid for internally smooth siphons that aren't too long.
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I thought this equation looked familiar. It is Toricelli's law, equally valid for a tank draining through an orifice:
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Yes, in the simple treatment of siphons the head loss in the pipe is neglected, which is OK for short, smooth siphons. Bear in mind though that for
siphons y is not the same as the fluid height in a tank.
Taking head loss into account makes it quite complicated, mathematically.
[Edited on 28-5-2016 by blogfast25]
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