Scratching my head... can you explain ?

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Externet

Joined Nov 29, 2005
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Hi. Your headache is back, again.

Can you explain, please ? ---->

Why the suction does not affect the discharge outlet ? :oops:
 

Papabravo

Joined Feb 24, 2006
20,154
Except that it appears to be syphoning from lower to higher. Could just be cleverly chosen camera angles.
Nothing wrong with that if you can just get it started. You just need to create enough vacuum to overcome the height difference between the surface of the liquid and the exit orifice. Above a certain height this is not possible. I'd have to look up the height of a column of water that can be supported by 1 atm of pressure at sea level.
EDIT: looks to be about 33+ feet
 

BobTPH

Joined Jun 5, 2013
6,527
Which can be done only if the outlet is lower than the inlet. Otherwise you are pumping water uphill with no energy input.
 

Papabravo

Joined Feb 24, 2006
20,154
Which can be done only if the outlet is lower than the inlet. Otherwise you are pumping water uphill with no energy input.
Pressure on a liquid water surface will support a column of water approximately 33' high. When you bend the pipe and create a vacuum the liquid will continue to flow.
 

BobTPH

Joined Jun 5, 2013
6,527
That part is true. But the pressure has to come from somewhere. In a siphon, it comes from the water flowing out, and it is only equal to the pressure difference over the distance it falls.

A siphon can lift water above the input reservoir only if it exits below that level.

Watch the second video, he demonstrates this effect.
 

cmartinez

Joined Jan 17, 2007
7,970
That part is true. But the pressure has to come from somewhere. In a siphon, it comes from the water flowing out, and it is only equal to the pressure difference over the distance it falls.

A siphon can lift water above the input reservoir only if it exits below that level.

Watch the second video, he demonstrates this effect.
yup ... it's actually quite simple:

1658106756837.png

The arrangement on the left is extracting gravitational potential energy from the differences in the liquid's level input vs its output. Aided by the push exerted by the atmospheric pressure, or course.

The arrangement on the right would require adding energy (i.e. a pump) to make it work, since it would be lifting the liquid above its stationary level.
 

WBahn

Joined Mar 31, 2012
28,497
Hi. Your headache is back, again.

Can you explain, please ? ---->

Why the suction does not affect the discharge outlet ? :oops:
Simple explanation -- they have a pump down in the well pumping water from the well up to the inlet pipe.

These types of videos are all fakes.

Just do a free body diagram of the system and track the pressure. What you will find is that the pressure in the inlet pipe is slightly lower than atmospheric, which will result in water being pulled up a small amount (perhaps a few inches -- there's a number of unquantified variables) but it physically can't pull it up all the way unless the end of the discharge pipe is below the surface level of the well.

A similar principle is at work with water coolers (the kind where you turn a 5 gal jug of water upside down). Imagine modifying one of those so that you had a valve coming out the side near the top (well, bottom when it's in the cooler). After putting it in the cooler, what would happen (initially) if you open that valve? Will water come of it? That would seem like what we would expect. But that's not what will happen. Air will flow in because the pressure at ALL points inside that jug that are above the open reservoir that's inside the cooler are below atmospheric pressure.
 

Wendy

Joined Mar 24, 2008
23,190
Siphoning is not over unity, so there is no need to close this thread. If you look closely at the first the first post you can see that the exit nozzle is lower than the concrete frame, in other words it's a camera trick.
 
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