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The capillary action's limit

by Yuri B.
Tags: action, capillary, limit
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Yuri B.
#1
Mar22-14, 12:54 PM
P: 125
Is it feasable to achieve elavation of water to, let's say, 10 m height due to the capillary action effect ? Or the capillary diameter for that to achieve should be less than the water molecules themselves ?
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Integral
#2
Mar22-14, 01:06 PM
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I do not believe that it is pure capillary action, but water does reach the top of 100m tall trees.
dauto
#3
Mar22-14, 01:49 PM
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Quote Quote by Integral View Post
I do not believe that it is pure capillary action, but water does reach the top of 100m tall trees.
That happens due to negative pressure at the top of the tree (otherwise known as tension). You might think a liquid cannot have negative pressure but that would be wrong. Water is actually in a metastable supercooled state at the top of the tree and would boil (due to negative pressure) if a nucleation seed was provided.

Watch Veritassium's youtube video titled "The Most Amazing Thing About Trees" for a clear explanation.

A.T.
#4
Mar22-14, 01:50 PM
P: 4,212
The capillary action's limit

Quote Quote by Integral View Post
I do not believe that it is pure capillary action, but water does reach the top of 100m tall trees.
The pores of the leaves (where the water evaporates) are indeed so tiny (2-5 nm), that capillary action is strong enough to balance the weight of the sap column below, within which the force is transmitted as tension (negative pressure) in the much thicker xylem-tubes (20000-200000 nm).

Yuri B.
#5
Mar23-14, 03:14 AM
P: 125
I meant artificial material.
UltrafastPED
#6
Mar23-14, 04:06 AM
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See http://www.lps.ens.fr/~balibar/Caupin-EPL08.pdf
"Absolute limit for the capillary rise of a fluid"
Yuri B.
#7
Mar23-14, 04:23 AM
P: 125
:
".........venerable question of why sap rises in tall trees [32]. We
hope to address this problem in future work"
A.T.
#8
Mar23-14, 05:08 AM
P: 4,212
Quote Quote by Yuri B. View Post
:
".........venerable question of why sap rises in tall trees [32]. We
hope to address this problem in future work"
See post #4. The xylem tubes in the tree stem are too wide to pull the water 100m by capillary action. But the much smaller pores in the leaves provide enough capillary action to balance the weight of the fluid column below, which is under tension.


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