Viscoty and Surface tension -- depends on the composition of the atmosphere?

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Discussion Overview

The discussion revolves around the relationship between surface tension and viscosity of fluids in relation to the composition of the atmosphere and the materials of the containers they flow through. Participants explore whether these properties are influenced by external factors such as gas composition and container material, touching on theoretical and experimental aspects.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants question why surface tension would not depend on the composition of the atmosphere, suggesting that different gases could alter the attraction between water molecules and gas molecules.
  • Others propose that the pressure at the gas-liquid interface is a more significant factor than gas composition itself.
  • One participant suggests that if a more dense fluid, like oil, is placed on top of water, the interactions at the interface could affect surface tension.
  • Concerns are raised about the viscosity of fluids flowing through different materials, with some arguing that the interaction between the fluid and the container could influence flow velocity.
  • Experimental evidence is mentioned indicating that the effects of container material on fluid velocity may not be significant, but this is contested by others who argue that "not significant" does not equate to "nonexistent."
  • There is a discussion about the implications of using terms like "zero" in fluid dynamics, with some participants advocating for more precise language regarding fluid behavior at boundaries.
  • One participant notes that the atmosphere can impact surface tension by dissolving into the fluid, which could lead to measurable changes depending on the gas composition.

Areas of Agreement / Disagreement

Participants express differing views on the significance of atmospheric composition and container material on fluid properties. There is no consensus on whether these factors have a measurable impact, and the discussion remains unresolved.

Contextual Notes

Participants highlight limitations in the discussion, such as the dependence on specific conditions and the need for precise definitions regarding fluid behavior and interactions.

Zohar
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why isn't Surface tension reliant on the composion of the atm?
For an instance; If you place a glass of water in a room with regular atmosphere or you place it in a room filled with other gasses. The coefficient of surface tension of the fluid will change? Maybe?

why isn't viscoty of a fluid reliant up on the the composition of the hose it flows in?
For an instance; blood flows in a vessel or blood flows in an aluminium hose. The velocity won't change?
 
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Welcome to the PF. :smile:

This is not my area, but from a quick Google search, it looks like the main affect would be due to the pressure of the gas at the gas-liquid interface, not so much the composition of the gas. This looks like a good article:

http://www1.lsbu.ac.uk/water/physical_anomalies.html#ST

1586121935955.png


Also paging @Chestermiller :smile:
 
Zohar said:
Summary:: why isn't Surface tension reliant on the composion of the atm?
why isn't viscoty of a fluid reliant up on the the composition of the hose it flows in?

why isn't Surface tension reliant on the composion of the atm?
For an instance; If you place a glass of water in a room with regular atmosphere or you place it in a room filled with other gasses. The coefficient of surface tension of the fluid will change? Maybe?
Why do you think it would?

why isn't viscoty of a fluid reliant up on the the composition of the hose it flows in?
For an instance; blood flows in a vessel or blood flows in an aluminium hose. The velocity won't change?
Why do you think the viscosity of a liquid would be affected by the vessel that it is flowing through?
 
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I think maybe if you change composion of air. The water will have diffrent attraction with the molecules of the gas the surface tension will change. Likewise the viscoty, when blood flows in a vessel it has some little attraction with it, and if you change the material it's flowing in, it maybe cause a change of velocity.
 
Last edited:
Zohar said:
why isn't Surface tension reliant on the composion of the atm?

Replace the 'atmosphere' with another fluid, more dense than air, laying on top - say oil floating on water. The interaction between molecules at the interface will be of a similar order to the internal interactions. ('Pour oil on troubled waters'?) . That will definitely affect the surface of the water and the formation of ripples and breaking waves so that's an obvious example of where the surface tension is reliant.
 
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Zohar said:
I think maybe if you change composion of air. The water will have diffrent attraction with the molecules of the gas the surface tension will change. Likewise the viscoty, when blood flows in a vessel it has some little attraction with it, and if you change the material it's flowing in, it maybe cause a change of velocity.
Experimental evidence indicates that this is not significant. The velocity of the fluid at the wall is, of course, zero (non-slip boundary condition).
 
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M
Chestermiller said:
Experimental evidence indicates that this is not significant. The velocity of the fluid at the wall is, of course, zero (non-slip boundary condition).
Not significant is obviously not the same as nonexistent -- it's not really quite non-slip -- it's almost non-slip -- and once again I'd like to be fussy about linguistic abuse of the term 'zero' -- to me, at least, negligibly greater than zero is not the same as zero, and I think that we shouldn't just complacently call a minuscule non-zero quantity zero, even if it's convenient to do so,
 
sysprog said:
M

Not significant is obviously not the same as nonexistent
As an engineer with extensive experience in solving real-world fluid dynamics systems, to me it is.
 
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Chestermiller said:
As an engineer with extensive experience in solving real-world fluid dynamics systems, to me it is.
I understand well that some engineers, if it helps to get real world problems solved, aren't shy about using linguistic shortcuts in their descriptions of what's going on.
 
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sysprog said:
I understand well that some engineers, if it helps to get real world problems solved, aren't shy about using linguistic shortcuts in their descriptions of what's going on.
Would you also include the effect of the gravitational pull of Jupiter's moons on the fluid flow behavior? It certainly is not exactly zero either.
 
  • #11
Chestermiller said:
Would you also include the effect of the gravitational pull of Jupiter's moons on the fluid flow behavior? It certainly is not exactly zero either.
Yes, I would indeed -- I tend to be rather more loquacious than terse. Here's a link to some work of my favorite fluid dynamics person: https://www.researchgate.net/scientific-contributions/2058879443_Qin_Yang. She's nice.
 
  • #12
Stepping around the dispute about the difference between 'negligible' and zero - to the OP:

The atmosphere can have an impact on the surface tension of the fluid because (for your proposed example, assuming equilibrium) the fluids are effectively different. The gas will dissolve into the water - that changes the fluid. Depending on the gas(es) you select for your 'alternative atmosphere', that change may be readily measurable.
 
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