Syphon or Siphon - but the dictionary is wrong anyway.
Syphon or Siphon - but the dictionary is wrong anyway.
(OP)
An interesting news item today in Australia's Sydney Morning Herald.
I wasn't sure where this would be best placed but as this forum is read by many who read and contibute to other forums guess this is as good as any.
http:// www.smh.co m.au/enter tainment/b ooks/dicti onary-mist ake-goes-u nnoticed-f or-99-year s-20100510 -uoh2.html
I wasn't sure where this would be best placed but as this forum is read by many who read and contibute to other forums guess this is as good as any.
http://





RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
Ted
RE: Syphon or Siphon - but the dictionary is wrong anyway.
Enjoy this,
http://www.aip.org/pt/feb00/maris.htm
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
Ted
RE: Syphon or Siphon - but the dictionary is wrong anyway.
... nothing to worry about, I'm sure.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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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.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
RE: Syphon or Siphon - but the dictionary is wrong anyway.
jt
RE: Syphon or Siphon - but the dictionary is wrong anyway.
RE: Syphon or Siphon - but the dictionary is wrong anyway.
RE: Syphon or Siphon - but the dictionary is wrong anyway.
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
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
RE: Syphon or Siphon - but the dictionary is wrong anyway.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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:
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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.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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.
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.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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):
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.
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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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
ht
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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 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.
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.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
RE: Syphon or Siphon - but the dictionary is wrong anyway.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
http:
http://www.lmnoeng.com/Channels/InvertedSiphon.htm
RE: Syphon or Siphon - but the dictionary is wrong anyway.
I think at this point we should just call any old bent pipe a siphon, no matter which way its turned, and simply go with the flow.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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.
:) 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.
h
Now, is it octopi, octopuses, or octopodes????
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
Katmar Software
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RE: Syphon or Siphon - but the dictionary is wrong anyway.
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