Capillary action between parallel plates. 1

[logbook]

I have done some calculations of the capillary head between two parallel plates and get exactly half the height obtained for a circular capillary tube, given the same materials used in each and with the plate separation equal to the diameter of the tube. Could somebody confirm this for me please.

Now if the two plates are not rectangular but L shaped, with just a part of the L dipping into a liquid, would it be fair to say that the liquid would rise up between the plates then spread out horizontally as well until the maximum capillary head was achieved vertically? Would there be a practical limit to the horizontal spread or would it keep going until the fluid reservoir was exhausted or the end of the plates was reached? Given that only part of the L is in the liquid and there is an unsealed bottom to the plates, will any leak out the bottom of the plates.

In my application the plates would actually be slightly curved and less than 1mm apart. Such capillary action would be an undesirable feature.

 

[prex]

I confirm what you found: it's easy to show that the usual formula for a capillary tube h=4[σ]sin[α]/[ρ]d changes to h=2[σ]sin[α]/[ρ]d when two parallel plates are involved at distance d.
However this would be valid if the borders of the two plates are closed (joined): otherwise more free surface develops, that, if of non negligible extension, should be included in the calculation and would modify the formula above.
Concerning your questions on spreading I guess that the liquid would spread out horizontally to the plate borders (as this doesn't consume potential energy), and would not spill out. A test wouldn't solve the mistery?

prex

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