What Are Negative Absolute Pressures in Fluid Mechanics?

[xxChrisxx]

For Liquids :
Liquids have Surace Tension -- Correct. But the Surface Tension as rightly discussed is only a phenomena observed on the surface of the liquid due to the unbalanced cohesive forces acting on the surface molecules from within the subsequent layers below the surface and the adjacent moleccules on the surface.

This does not mean that the liquid can Sustain tensile force/stress. This is actually a pulling force or -ve force applied above the surface. And what it does is creates a pressure lower than the exsisting pressure of the liquid or what we call is partial vacuum.
Under the influence of such pressure the liuqid will simply start to Vaporize if the pressure reaches the required saturation pressure for the given tempreature.

Thats just it liquids CAN sustain tension under certain conditions. Which is why I didnt really want to go there, because it then raises the question of negaive absoulute pressures. And that's a whole can of worms.

So we say that a gas is subjected to a PRESSURE rather than a Stress

I'd tend to use pressures all fluids, I don't like using stress becuase fluids can flow (it can't support shear) amd Pressures are also measured which stresses arent. But although I don't really like it, there is no reason why you can't use tension and compression for fluids (included gases) It would be pointless for gases becuase as you say they flow and react to external pressure change.

 

[ank_gl]

For Liquids :
Liquids have...
..
So we say that a gas is subjected to a PRESSURE rather than a Stress

I completely agree.

there is no reason why you can't use tension and compression for fluids (included gases) It would be pointless for gases becuase as you say they flow and react to external pressure change.

I completely agree to this too.

Although I don't see any reason to mix the two different terminologies relating to different subjects.

 

[xxChrisxx]

There isnt, as this thread shows it only leads to confusion.

 

[nanunath]

Oh...
So much to read since my last visit...

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