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siphon : ウィキペディア英語版
siphon

The word siphon (from "pipe, tube", also called syphon) is used to refer to a wide variety of devices that involve the flow of liquids through tubes. But in a narrower sense, the word refers particularly to a tube in an inverted 'U' shape, which causes a liquid to flow upward, above the surface of a reservoir, with no pump, but powered by the fall of the liquid as it flows down the tube under the pull of gravity, then discharging at a level lower than the surface of the reservoir it came from.
There are two leading theories about how siphons cause liquid to flow uphill, against gravity, without being pumped, and powered only by gravity. The traditional theory for centuries was that gravity pulling the liquid down on the exit side of the siphon, resulted in reduced pressure at the top of the siphon. Then atmospheric pressure was able to push the liquid from the upper reservoir, up into the reduced pressure at the top of the siphon, like in a barometer or drinking straw, and then over.〔〔〔〔 However, it has been demonstrated that siphons can operate in a vacuum〔〔〔(Duane1902 )〕〔〔 and to heights exceeding the barometric height of the liquid.〔〔http://www.youtube.com/watch?v=sz9eddGw8vg Siphoning water to 24 meters〕 Consequently, the cohesion tension theory of siphon operation has been advocated, where the liquid is pulled over the siphon in a way similar to the chain model.〔https://www.youtube.com/watch?v=6ukMId5fIi0 Bead Chain Siphon〕 It need not be one theory or the other that is correct, but rather both theories may be correct in different circumstances of ambient pressure. The atmospheric pressure with gravity theory obviously cannot explain siphons in vacuum, where there is no significant atmospheric pressure. But the cohesion tension with gravity theory cannot explain CO2 gas siphons,〔https://www.youtube.com/watch?v=FWybQPxKy1U CO2 Gas Siphon〕 siphons working despite bubbles, and the flying droplet siphon, where gases do not exert significant pulling forces, and liquids not in contact cannot exert a cohesive tension force.
All known published theories in modern times recognize Bernoulli's equation as a decent approximation to idealized, friction-free siphon operation.
==History==
Egyptian reliefs from 1500 BC depict siphons used to extract liquids from large storage jars.〔http://www.moundtop.com/pdf/AncientWinemaking.pdf〕〔http://books.google.com.au/books?id=xuDDqqa8FlwC&q=siphon#v=snippet&q=siphon&f=false〕
There is physical evidence for the use of siphons by Greek engineers in the 3rd century BC at Pergamon.〔〔Dora P. Crouch (1993). "''(Water management in ancient Greek cities )''". Oxford University Press US. p. 119. ISBN 0-19-507280-4〕
Hero of Alexandria wrote extensively about siphons in the treatise ''Pneumatica''.〔http://himedo.net/TheHopkinThomasProject/TimeLine/Wales/Steam/URochesterCollection/Hero/index-2.html〕
In the 9th century, the Banu Musa brothers invented a double-concentric siphon, which they described in their ''Book of Ingenious Devices''.〔http://www.history-science-technology.com/articles/articles%2011.html〕 The edition edited by Hill includes an analysis of the double-concentric siphon.
Siphons were studied further in the 17th century, in the context of suction pumps (and the recently developed vacuum pumps), particularly with an eye to understanding the maximum height of pumps (and siphons) and the apparent vacuum at the top of early barometers. This was initially explained by Galileo Galilei via the theory of ''horror vacui'' ("nature abhors a vacuum"), which dates to Aristotle, and which Galileo restated as ''resintenza del vacuo,'' but this was subsequently disproved by later workers, notably Evangelista Torricelli and Blaise Pascal – see barometer: history.

抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)
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