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Syphon or Siphon - but the dictionary is wrong anyway.
6

Syphon or Siphon - but the dictionary is wrong anyway.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

The article was interesting enough, but the comments make even more interesting reading.  It is sad to see how non-technical people regard the search for accurate knowledge as a waste of time and money.

According to Wikipedia, it is the "tensile stength" of liquid water that makes a water siphon work in a vacuum.  I will have to think about that one.  But somehow this "tensile strength" won't allow water siphons with a rise of 15m. Very confusing.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Ah yes.  The ancient woe of facing two bad choices:  Like the Greeks trying to sail the strait and narrow between Syphon and Charyllis ...  

Either can sink a wit (er, ship.)

RE: Syphon or Siphon - but the dictionary is wrong anyway.


It is generally assumed (Bernoulli) that the minimum pressure is at the summit of the siphon or just downstream, and if it equals the vapor pressure of the fluid in question the priming may be lost limiting the height of the siphon.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Sure, it's a form of tensile strength in play, when you suck the fluid up the piping to prime the siphon in the first place.   

And it's related to the vapor pressure of the fluid at the temperature of operation, so if you had a fluid with a high vapor pressure, sucking on the piping would cause the fluid to vaporize, thereby preventing priming and siphoning.

TTFN

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RE: Syphon or Siphon - but the dictionary is wrong anyway.

Once again having a PhD does not mean you know what you are talking about or even understand how to research to gain knowledge.

Ted

RE: Syphon or Siphon - but the dictionary is wrong anyway.

2
The tensile strength of water is rather important in nature: the height of trees is determined by water's tensile strength. Otherwise, trees would not exceed 33 ft in height.

Enjoy this,
http://www.aip.org/pt/feb00/maris.htm

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Sucking does not pull the water.  Sucking creates a pressure lower than atmospheric pressure at the other end, the unbalanced force then pushes the water up the pipe.  Try pulling water uphill through a partially filled pipe.

Capillary action in trees depends on the surface tension of the water to pull the water up.  When to tube is too large, the weight of the water is greater than force the surface tension can pull.

Ted

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Actually nobody said "sucking pulls up" the water.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Then I mis-read IRstuff.

Ted

RE: Syphon or Siphon - but the dictionary is wrong anyway.

I know he wasn't implying that.
... nothing to worry about, I'm sure.

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.

trees on high mountains would only be 16 ft high.  

**********************
"The problem isn't finding the solution, its trying to get to the real question." BigInch
http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.


Think about chemical potential as the driving force.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

"tensile strength of water"

That is an analogy I don't think should be promoted (reworded:  that's dumb!).  Keep it up and we'll have people asking us if they can heat treat their water to improve its tensile strength.  And then people telling us not to drink from pumped water systems, since the cyclic loading from the pump "fatigues" the water...

 

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Oh yeah.  Water has, after all, the chemical potential to be converted to, or mixed with, EtOH.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

No wonder I've been feeling tired! I've been drinking fatigued water! Back to beer for the energy boost I need!

jt

RE: Syphon or Siphon - but the dictionary is wrong anyway.

or mix water with CH3CH2OH, chill and enjoy

RE: Syphon or Siphon - but the dictionary is wrong anyway.

A siphon works by the difference in pressure between atmospheric pressure (gravity) pushing on the water surface and the negative pressure caused by the water column on the downstream leg. It has nothing to do with water tension - a siphon will operate with air pockets. The dictionary is correct.   

RE: Syphon or Siphon - but the dictionary is wrong anyway.

What drive the liquid through the syphon is the difference between the column pressures due to the different heights of the two legs, ie the well known

  Pressure = ρ x g x h  (Density times gravity times height)

So it is gravity that drives a syphon.  The role of the atmospheric pressure is simply to ensure that the pressure at the apex of the syphon does not go below the vapor pressure of the flowing fluid.  The atmospheric pressure is equal at the inlet and outlet of the syphon, so it cannot cause the flow.

I do no buy the "tensile strength" argument.  I am not a botanist, but I suspect that the way a tree gets water to heights above 10 meters has more to do with the xylem capillaries working as millions of little pumps in series than to do with "tensile strength" of a liquid.  I have seen that when you half fill a syringe with water and close the outlet with a finger you can easily withdraw the plunger further - all that happens is that the water boils and there is no "tensile strength" in evidence.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Syphon or Siphon - but the dictionary is wrong anyway.

As I recall, at last some trees have check valves that, once water makes it up some part of the way, the valves close then it can get a bit farther.

So, syphons don't work in a vacuum then, heh?
How does NASA move fuel from tanks to pump suction before its sent on to the combustion chambers under pressurized flow.

**********************
"Being GREEN isn't easy" ..Kermit
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http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Spacecraft with large liquid fuel tanks use small control jets to accelerate the craft enough to move the fuel to one end of the tank before starting the main engine.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

This thread is a little lost in semantics. water is moved by pressure difference - it is pushed not pulled. water tension is not relevant. In a siphon a negative pressure is created on the downstream leg by the weight of water dropping down the column. We could equally well create a suction by pulling a plunger down the downstream column. (we would then call it a vacuum pump). The motive force is atmospheric pressure acting on the water surface which pushes the water through the siphon. Atmospheric pressure is 32 ft head of water and hence this is the maximum head on a siphon - regardless of how long the downstream leg is.

Water rise in tress is by capillary action (tension) and there is no limit to the rise. If the capilary attraction between the water and the capillary is greater than the weight of water in te capillary/unit length then there is no limit, hence 400 ft high redwoods with no non-return valves. The motive force is evapotranspiration - a very small tension caused by a vacuum at the leaves causes water to rise the full height of the tree.    

RE: Syphon or Siphon - but the dictionary is wrong anyway.

PS The dictionary is correct.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

BRIS - I can't see how there can be a capillary action per unit length. If the capillary is full, how does the capillary action "know" to pull up and not down?  I can only see capillary action occurring at the top surface.

Also, if water can only move by being pushed and not by being pulled (which I agree with) what is the relevance of "evapotranspiration - a very small tension caused by a vacuum at the leaves".  I can see that evaporation is necessary to create the vapor liquid interface that is at the heart of capillary action (in my understanding) but how does this "very small tension" result in water being pushed/drawn up 400 ft?

I don't mean to attack you with these question.  I have little/no knowledge of botany and I am trying to understand how water rises to great heights in a tree. I have Googled and read many web pages, but botanists seem to have as little understanding of hydraulics as I do of botany. They all talk of the water being pulled up the tree.  At this stage the multi-pump pipeline model, combined with BigInch's natural non-return valves, seems the most plausible to me.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Nobody remembers the water and mercury experiments from H.S. Physics.

If the minuscus curves up, force and movement due to surface tension is up; water.  If the minuscus is down, force and movement due to surface tension is down; mercury.

http://en.wikipedia.org/wiki/Meniscus
http://en.wikipedia.org/wiki/Capillary_action

Apparently the limit for [b]trees[b] is 427 ft (130 m),
http://www.davidlnelson.md/Cazadero/Trees&;CapillaryAction.htm

**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.


Bris, consider two vessels at different levels connected with a flexible hose and containing water at constant (say overflowing) levels. You will agree that water will flow from the higher to the lower container by gravity.

Now, push up the middle of the flexible conduit to a height above the water level on the upper container, and you"ll see that flow continues... possibly slightly reduced by a small increase in friction. You have a siphon operation.

QED: it is gravity that forces the flow, not atmospheric pressure, as Katmar rightly said.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

BASIC FLUID STATICS REVIEW

Forgetting surface and any other liquid tension forces for the moment, total pressure of a fluid column is caused by an acceleration on the mass of the fluid (accelaration + gravitational accelerations, where gravity exists) [b]plus[b] any other absolute pressure acting on its surface.  Total pressure is not caused by acceleration alone.

Flow in a pipe is caused by an absolute force difference between the ends of the fluid column - frictional force;  (Divide by x-sectional area to get pressure).  Whether the pressure at either end of the fluid column is caused by acceleration acting on a fluid column's mass (when there is accelerations to account for), or the absolute pressures at each end of the column (if they are not perfect vacuums), AND/OR the sum of BOTH, is irrelevant.  It is not one or the other, it is the sum of both - friction that drive any movement of the column, When the sum of both - friction  due to flow is = 0, movement is occuring.  When the sum of both (and there is no friction) = 0, no movement is occuring.

The attached spreadsheet clear shows how and when flow occurs by pressure imbalance caused by the combination of acceleration and absolute pressures at the end of the pipe, whether there is a siphon involved or not.  Change the value of the height of PIPE TK2, and/or the ABSOLUTE PRESSURE IN TANK 4, and the direction of flow is calculated and shown under tank 2.  If the height of PIPE TK2 is less than the fluid elevation in Tank 1, you could say a siphon is occuring, otherwise you'd probably just say its "gravity flow", although gravity flow technically only exists (usually in open channels) where the pressure on ALL the surface of a fluid is CONSTANT.  That being the case, the only mechanism for driving flow is acceleraton, or gravity if you will, or wind driven waves shoaling up on the beach, etc., but that is to remain outside of my discussion today.

Please be a little careful when changing other input values.  There are a few error checks, but this spreadsheet isn't "idot proff".  It would be better if you don't use negative numbers without thinking of the etended implications and please try to keep the tanks on the side of the lines as drawn.

OK, now back to water tension as a mechanism for driving flow when gravity and other accelerations do not exist and the temperature is kept below the fluid's bubble point at any given pressure.

**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco

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RE: Syphon or Siphon - but the dictionary is wrong anyway.

25362 (Chemical)

Atmospheric pressure is a result of gravity - gravity is pulling the water down the downstream leg which leaves a partial vacuum behind, Atmospheric pressure on the upstream pushes water into the Vacuum. i,e across a datum line there is an imbalance of pressure between atmospheric on the inlet and a reduced pressure on the outlet. The water column on the outlet is acting as a plunger pulled down by gravity. Atmospheric pressure on the inlet is pushing the water into the negative zone. I have designed many air regulated siphons that operate with an air/vapour phase n the outlet.   

RE: Syphon or Siphon - but the dictionary is wrong anyway.

If you do not have gravity, the longer leg will not flow(drain).  Therefore it's gravity.
Wait.  If you do not have atmospheric pressure, the shorter leg will not flow(fill).  Therefore it's pressure.

Like Biginch is saying, the siphon depends on both pressure and gravity.

25362, if you try your exercise with a flexible open channel, your argument fails.  The same would be said of a partially full pipe.  The need for a full pipe is so a seal occurs and intake pressure can push.

Ted

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Hytools

Yes atmospheric pressure  pushes the water over the hill that is why the dictionary is correct. The water then falls down the other side by gravity.

in an air regulated siphon we bleed air into the crest to control the flow rate.  

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Tank you [b]hydtools![b].

Atmospheric pressure IS the result of gravitational acceleration on the earth's atmosphere.  Gas pressure in tank 1 in my spreadsheet is not affected by gravity, as it is outside any gravitational field of influence.  It is not an atmosperic pressure.  The gas pressure in tank1, as is in any tank not affected by gravity in outer space, is the result of the kinetic energy of the gas alone ∑ 1/2 mv^2.  If it was affected by gravity, the gas pressure at the bottom of the tank would be 14.7 + ρ_gas  * g * height of the tank.

BRIS, you well may have designed a siphon that works with some pressure lower than atmospheric pressure at the gooseneck, which would draw in air from an open valve and you may have reguated water flow into the gooseneck riser by effectively increasing the pressure at the gooseneck by allowing that higher atmospheric pressure to leak in through the valve placed there (thereby reducing the pressure drop in the riser) and lowering its flowrate, but you have not designed one where the pressure at the gooseneck was at or below the vapor pressure of the water.

**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.

To hydtools, the conduit is full (primed, as I said in a previous posting), otherwise, the siphon may be broken.

BRIS: The reduced pressure at the (full) constant-diameter conduit summit in a siphon is the result of a mechanical-energy balance, as in any other pipe, expressed by the well-known Bernoulli equation for incompressible fluids w/o friction. Keeping the kinetic energy constant, if you gain height, you lose pressure, and viceversa. In short, no energy accumulation.

For a given flowrate in a horizontal pipe (z1 = z2) of increasing diameters you lose velocity head (V1>V2) and gain pressure head. Which shows that the flow advances against increasing pressure heads.

Using dimensions of length or height for pressure head, velocity head and elevations (z):

p1/ρg + V12/2g + z1 = p2/ρg + V22/2g + z2

In case the flowrate and the diameter are constant (V1 = V2), an increase in elevation z2>z1, the pressure will go down p2> p1 to balance mechanical energies.

Please notice the effect of changes of the density ρ on the balance.
 

RE: Syphon or Siphon - but the dictionary is wrong anyway.


I should have written p2 < p1.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Learned something about space fuel systems.
Some are as compositepro said; A submerged pump is in the fuel storage tank and stores some fluid on shutdown used for firing up and accquiring an initial acceleration later on.  But it does seem to be more common to use only the pressure of the fuel tank to reach the pump.  No mention of liquid tension being considered.

http://www-rohan.sdsu.edu/~sharring/Launchvehiclepistonless2004-7004.pdf

**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.


On the subject of liquids under tension (metastability) and the ascent of sap in trees, I recommend reading Pablo G. Debenedetti's Metastable Liquids Concepts and principles, Princeton University Press.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Take a class - fill it with water - place a thin card on top and turn it upside down, the water remains in the glass - is this atmospheric pressure or gravity.?

Take a siphon close a valve on the outlet - the siphon remains primed - is this atmospheric pressure or gravity.?

Water flows down a pipe by gravity it surmounts a siphon crest by atmospheric pressure pushing it over.

Flow through a siphon is dependent on atmospheric pressure and the maximum height of the rising limb would be less at altitude.

Gravity affects everything without gravity we would not be able to hold the water in the pond in the first place.

The dictionary is still correct !!

RE: Syphon or Siphon - but the dictionary is wrong anyway.

PS - I have not designed siphons with dynamic pressures below vapour pressure. The maximum crest height of a siphon is atmospheric pressure (32 ft) - vapour pressure.


I have designed siphons that prime by evacuating air out of the downstream leg - is the water then sucked over the crest by tension or is it pushed by atmospheric pressure ?

If you had no atmosphere but still had gravity a siphon would not work !

 

RE: Syphon or Siphon - but the dictionary is wrong anyway.

If there is acceleration, its acceleration, if there is pressure, its pressure, if there are both, its both.  If pressure is due to gravity ρ*g*h, or ∑1/2 mv^2 of the gas molecules is irrevelant, its the sum  = total head (as energy) of an external fluid that supplies the motive force to the fluid within the siphon.

I've commented to the article in the newspaper as follows,
====================================================
Dr. Hughes isn't entirely correct, in fact still about as erroneous as the original definition.  The definition in the dictionary was correct for its time, when travel outside the Earth's gravational field was not seriously contemplated.  While still correct on Earth, there is no doubt that it needs to be updated for modern times by replacing its reference to atmospheric pressure with the sumation of the molecular kinetic energy, 1/2 mv^2 + pressure, p*g* h, of the external gas supplying force to a siphon.  These days, it is not limited to either Earth's gravity or atmospheric pressure.  Gravity could be replaced by acceleration of a spaceship and atmospheric pressure by a connection to any external pressure source, such as the atmosphere in a space ship.

**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco

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RE: Syphon or Siphon - but the dictionary is wrong anyway.

Sorry to come in a so long thread, but really can't see why a siphon could not, in principle, work in the absence of atmospheric pressure.
Granted that any real liquid will vaporize at zero absolute pressure, making the siphon behavior impossible, but we can easily imagine, without breaking any fundamental law, of an ideal fluid that, just like many solids, would not vaporize in vacuum, or at least would at a very low rate (like solids that sublimate).
Gravity, on the contrary, is intrinsically and in principle, required (in a stationary system), just because is the loss in potential energy of the fluid that makes it possible to overcome friction losses associated with fluid flow.
So I'm more with the position that siphons are gravity fed (in a stationary system) than they are fed by atmospheric pressure.

prex
http://www.xcalcs.com : Online engineering calculations
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RE: Syphon or Siphon - but the dictionary is wrong anyway.

Of course they can work in the absense of external pressure.  External pressure is only one component of potential energy, or head, acceleration being the other.  A siphon would work if you have either one of them, or both.  A siphon simply converts some potential energy to the kinetic energy of motion of the fluid within. Where they won't work is where there is zero potential energy, no 1/2 mv^2 or acceleration.

What I totally fail to understand is why that debate continues.  Can anybody explain why they do not choose to accept Bernoulli's theory and back it up with a spreadsheet calculation of an example why it does't work?  

I think it would be more productive use of remaining time to discuss if a siphon could continue, after being started, due to liquid tension effects, if net pressure and accelarations drivers suddenly became nil.      

**********************
"Being GREEN isn't easy" ..Kermit
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RE: Syphon or Siphon - but the dictionary is wrong anyway.

Well, if you have a glass full of water next to an empty glass, and have a cotton string string draped into both, then the water will rise up the string by capillary action (surface tension) and drop into the empty glass due to gravity plus capillary action. The level in the two glasses will equilibrate. In this example, clearly, no air pressure is involved. However, I don't think it would be correct to call it a siphon.

If you have a chain in a bucket that rises to a pulley and then drops into a lower bucket would that be called siphon?

Another interesting example: in a pool of fresh water you submerge a container of salt water (higher density than fresh). If a tube is draped over the edge of the bucket to a lower level nothing will happen if the tube is filled with fresh water. "Prime" it with salt water and the salt water will flow out of the bucket. There is no air pressure involved and no interfacial surface tension. Since all liquids, by definition, have surface tension, you can do the same experiment with  two gasses with differing density.

The siphon principle is not about what makes fluids flow down-hill. It is about what makes it go up first. In most practical siphons it is air pressure pushing the liquid.  

RE: Syphon or Siphon - but the dictionary is wrong anyway.

That's  only because it is much easier to provide the necessary potential energy differential by changing the pressure, rather than changing acceleration.  However, if you fitted a siphon hose to the side of a gas tank and began spinning the apparatus about the vertical tank axis, until flow would initiate within the tube as the result of centripital acceleration forcing the gasoline to flow up towards the gooseneck, cross over and flow downwards thereafter, at which time you could stop rotation and flow would continue without further aid.  No change in atmospheric or siphon outet pressure would have been necessary for initiation.

**********************
"Being GREEN isn't easy" ..Kermit
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RE: Syphon or Siphon - but the dictionary is wrong anyway.

Is there any real dispute that once a siphon is primed it is gravity pulling the water down the downstream leg that creates a negative pressure which gives a pressure differential allowing air pressure to push water over the hump.

In "gravity" pipes and siphons water flows from a higher to lower elevation by gravity  - the feature of a siphon, (as it is traditionally understood) is that water first goes uphill, and unless anyone really believes that this is achieved by tension in the water, it clearly goes uphill due to the difference in pressure between atmospheric pressure at the inlet and the less than atmospheric pressure at the crest.

 

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Bris - if the siphon is fully primed, then it is acceleration due to gravity or any other source (of acceleration) that does it and it has very little to do with atmospheric pressure. In fact, I have never seen a siphon initiate simply because of atmospheric pressure differences. In normal situtations, such as on earth and not spinning rapidly - it requires either a) artificial suction on one end, b) pressure on one end or c) full priming to begin a siphon which will then continue simply due to gravitational acceleration.

RE: Syphon or Siphon - but the dictionary is wrong anyway.

The only "dispute" I have is that you're seeming to say that the only thing that can give rise to potential energy is gravity.  That would ignore the other terms in Bernoulli's theorm and seemingly prohibit siphons in weightless conditions, which obviously can exist where a gas pressure, not caused by gravity (as is atmospheric pressure), provides the potential energy difference that continues the flow.  Other than that, nothing else I can put my finger on.

**********************
"Being GREEN isn't easy" ..Kermit
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RE: Syphon or Siphon - but the dictionary is wrong anyway.

One step past Bernoulli, you could heat an expansive liquid in a closed container, even with no driving gas pressure, until fluid was forced up a siphon in a direction opposite a net acceleration and then let heat and acceleration continue the flow over the gooseneck, or remove the acceleration if you like, and allow the flow to continue as long as the fluid continued to expand due to heat alone.  In that case only heat would provide the required potential energy by increasing the molecular kinetics of the liquid, which was responsible for its expansion to begin flow.

**********************
"Being GREEN isn't easy" ..Kermit
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RE: Syphon or Siphon - but the dictionary is wrong anyway.

It is certainly possible to move a liquid through a pipe by applying a gas pressure to one end of the pipe, as was done traditionally with acid eggs.  And of course this can be done whether we have gravity (or any other form of acceleration) involved or not - only the magnitude of the required pressure differential would change.  But I would not call that a syphon.

For my money, to be termed a syphon the system must take advantage of the natural tendency of liquids to flow from a source at a higher level down to a lower level under the influence of gravity, but with the added requirement of having to flow via a third level that is higher than the source level.

Further, I would say that if there is no external atmospheric pressure that prevents the liquid from boiling at the apex of the syphon you do not have a true syphon system.  The direction of the force of gravity (or other acceleration) would cause the liquid to flow away from the apex, and it is only the external atmospheric pressure that prevents boiling.  As soon as boiling occurs the liquid heights in the two legs equilibrate and flow stops.

Many different flow systems, from ancient trees to modern space vehicles, have been described in this thread and while they may indeed cause liquid to flow from one point to another I would not call them syphons unless these two requirements are met.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Katmar, "at a higher level down to a lower level under the influence of gravity, but with the added requirement of having to flow via a third level that is higher than the source level."

Why limit yourself to "gravity"; when it is the effect on the liquid that could be caused by any applied acceleration which gives the potential energy needed to make it work.  Flow moving through a waypoint "higher than the source", yes, but higher in relation to what?  In space there is no higher or lower level.  Define it with respect to the direction of acceleration and a siphon can exist using the remainder of your definiiton.

Further, what's your fixation with pressure caused by atmospheric pressure and is it relavent to whether a siphon flows or not.

I think you would probably have a different view of things, if you got your head off the ground.  Can a siphon work in an airplane?  Can it work when its flying upside down?  Can it work when its upside down while flying a weightless trajectory?  Can it work while executing a loop; at the top of the loop, a 9G loop.  There you have it, Earth gravity is ony 1G, so 10G would be caused by centripital acceleration and -1G by Earth gravity.  Net 9G "up" and reduced atmospheric pressure at 10,000 feet, causing flow to go up the normally "downward" pointing downspout.  Now go to a U2 at 100,000 feet. Take the next step.  Where do you draw he line?  Earth's gravity technically never goes to zero, only approaches zero until you get somewhere near another body that has a gravitational attraction greater than Earth's and the net gravitational vector flips the other way.  smile

**********************
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RE: Syphon or Siphon - but the dictionary is wrong anyway.

I like katmar's definition, however it does not address an inverted siphon, used commonly (well not all that commonly) on sewer mains which go under a crossing obstruction such as a river, freeway, or another pipe. These siphons travel through a third level that is lower than the source. I'm not sure if they are truly siphons at all and am sure we will not decide it on this forum.

http://search.yahoo.com/search?ei=utf-8&fr=slv8-&amp;p=inverted%20siphon&type=

http://www.lmnoeng.com/Channels/InvertedSiphon.htm

RE: Syphon or Siphon - but the dictionary is wrong anyway.

now I keep hearing that BP is siphoning off the oil through a long thin tube to the bottom of the gulf. I have seen numerous news reports showing a schematic of the "siphon".  Care to comment on if this is truly a "siphon"

RE: Syphon or Siphon - but the dictionary is wrong anyway.

If its a bent pipe, I'll bite.

I figure it probably goes up to the surface, then goes higher, crossing over the top of the tanker's hull before turning back down and going below sea level into the tanks, thereby officially qualifying to be a "siphon" or perhaps  a "syphon", by anybody's definition, since unfortunately, this is happening on Earth and within its gravational field.

Not trying to give anyone a hard time, only to find a bit of humor in a very bad situation. Apologies in advance.  

**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.

BigInch - Yes, the gravity could equally be some other acceleration and I mentioned this several times in my "definition". Of course by "higher" I meant in the direction of the acceleration.

You cannot have a syphon if the atmospheric pressure is insufficient to prevent boiling at the apex.  This was one of the first points made (by 25362) right at the top of the thread.  If this were not so you could have the apex of a water syphon (on earth!) more than 10 meters above the source level, and we all know that is impossible (barring capillary action).

And if you want to operate a syphon under a gravity (whoops, I mean acceleration) of 10G you need a proportionally higher atmospheric pressure.

cvg - I would not call an "underpass" a syphon, but I know what you mean.  Also I think that the use of the word "syphon" in regard to BP's activities in the gulf is more akin to the figurative use of the word as in "my bank syphons money out of my account disguised as service fees" than to the literal sense of "some thief syphoned the gas out of my car".  Please note that there is no hidden meaning in the fact that I use the words "bank" and "thief" in the same sentence.

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

RE: Syphon or Siphon - but the dictionary is wrong anyway.

Why must there be atmospheric pressure?  Pressure is pressure.  Pressure level?  Just keep the temperature below the bubble point for any pressure you happen to have at the gooseneck and you won't vaporize.  I only thought vaporization was prohibited if you wanted to consider tension force.  Besides, you could have partial vaporization, with a vapor bubble forming at the top of the pipe and liquid flow underneath it.  Would that not be a siphon?  You could have a vapor bubble form across the entire cross section and, if the velocity was fast enough to carry it down below the bubble point line in the downcommer, before the siphon "broke", it would be a 2phase flow siphon.  If the bubble reached a high enough pressure to collapse as it was swept down the liquid column, it would go back to one-phase siphon flow.

**********************
"Being GREEN isn't easy" ..Kermit
http://www.youtube.com/watch?v=hpiIWMWWVco

http://virtualpipeline.spaces.live.com/

RE: Syphon or Siphon - but the dictionary is wrong anyway.

katmar, inverted siphon is not my word - it is a published and frequently used term. I have not heard any other term used to describe what you call an underpass. It is published in the following dictionary:

Sci-Tech Dictionary
McGraw-Hill Dictionary of Scientific and Technical Terms, 6th edition, published by The McGraw-Hill Companies, Inc.

http://www.answers.com/topic/inverted-siphon

RE: Syphon or Siphon - but the dictionary is wrong anyway.

If its a bent pipe, I'll bite.

:)  Author Terry Pratchett (I think) once described all life as being a bent tube.  So, a python is a syphon, and it'll certainly bite...though you may disagree:

Is a perstaltic python a syphon?

RE: Syphon or Siphon - but the dictionary is wrong anyway.

cvg - Thanks for the link confirming the inverted siphon terminology.  I followed their link to ordinary (non-inverted) siphons and they confirm the requirements of gravity and atmospheric pressure. See http://www.answers.com/topic/siphon

Katmar Software
Engineering & Risk Analysis Software
http://katmarsoftware.com

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