Capillary and liquid tension problem

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Discussion Overview

The discussion revolves around a capillary system involving two tubes of different diameters and the behavior of liquid in response to changes in pressure and surface tension. Participants explore the concepts of capillary action, pressure differentials, and the effects of surface tension on liquid movement within the system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes a capillary system where a thinner tube is full of liquid while a larger tube has a meniscus, questioning the underlying physics of the system's behavior.
  • Another participant references the Young–Laplace equation, suggesting it may be relevant to the discussion.
  • The original poster asks for clarification on why the larger tube has a taller liquid column at equilibrium despite the thinner tube being full.
  • The original poster also questions why adding a drop to the thinner tube causes liquid to flow towards the larger tube, indicating a belief that a pressure differential is necessary for liquid movement.
  • One participant notes that the larger tube has smaller curvature, leading to smaller capillary pressure, and suggests that adding a drop creates a downward capillary pressure that influences liquid movement.

Areas of Agreement / Disagreement

Participants express uncertainty about the dynamics of the system, with some proposing explanations based on capillary pressure and surface tension, while others seek clarification on the underlying principles. No consensus is reached regarding the specific mechanisms at play.

Contextual Notes

Participants acknowledge the complexity of the problem, including the roles of surface tension and pressure differentials, but do not resolve the mathematical or conceptual uncertainties involved.

Who May Find This Useful

This discussion may be of interest to individuals exploring fluid dynamics, capillary action, or those seeking to understand the interplay between pressure and surface tension in liquid systems.

greyy
Dear all,
I have a problem to solve but i am not very familiar with physics.
See attached image.
Data:
1)I have a capillary system with a short an thinner tube on one end and larger taller tube communicating.
2) at the equilibrium, the thinner capillary is full of liquid, while there is a meniscus on the larger one.
3) when a drop is added on the top of thinner tube, system re-equilibrates flowing on the right, increasing the height in the right tube.

I assume total pressure on the left is higher than the pressure on the right.
But why is all happening?
surface tension on the left vs capillary forces on the right? (in a communicatin vessel system, nomally, the larger tube has lower liquid height, but here the thinner tube has no more walls.)..
Thanks in advance for any help!

Urla
 

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Dear haw, no. honestly. I've just given a read to the link, I am not getting.
Could you give me an explanation on the graphical example I provided?

Question 1, why at the equilibrium the larger tube has a taller liquid column compared to the thinner capillary (on left of the image)? I understand the thinner capillary is already full .

Question 2, when I perturb the equilibrium by puttin a drop on the top of the thinner capillary the liquid flows to the right. I understand that the drop has no real walls and it is just surface tension.. why is flowing to the right towards the larger capillary?

From my very limited physics knowledge, I remember that in order to have a movement of a liquid I need a delta Pressure. In this case P(@drop) > P(@larger capillary). At the equilibrium P (@thin capillary ) = P(@larger capillary)
 
Last edited by a moderator:
larger tube has smaller curvature, so capillary pressure is smaller. And add a drop, neglect gravity of this drop, you still add a capillary pressure downward
 

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