Does an ideal fluid have zero surface tension?

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Does ideal fluid have zero surface tension?
What does zero surface tension signify?

Answers and Replies

.Scott
Homework Helper
Does ideal fluid have zero surface tension?
The definition of an ideal fluid is only that it has zero viscosity. So it would be allowed to have surface tension and still be considered ideal.
What does zero surface tension signify?
It would signify that the molecules within the fluid have the same attraction to each other as to the atmosphere at the surface.
Here is a link to the wiki article:
https://en.wikipedia.org/wiki/Surface_tension

A near-zero surface tension also tends to indicate that the fluid will readily evaporate.
Surface tension decreases as fluid temperature increases.
Fluids with low surface tension include Diethyl Ether (17.0), liquid Nitrogen (8.5), and liquid Helium II (0.37). In contrast, mercury at 15C has a surface tension of 487.

Last edited:
The definition of an ideal fluid is only that it has zero viscosity. So it would be allowed to have surface tension and still be considered ideal.
It would signify that the molecules within the fluid have the same attraction to each other as to the atmosphere at the surface.
Here is a link to the wiki article:
https://en.wikipedia.org/wiki/Surface_tension

A near-zero surface tension also tends to indicate that the fluid will readily evaporate.
Surface tension decreases as fluid temperature increases.
Fluids with low surface tension include Diethyl Ether (17.0), liquid Nitrogen (8.5), and liquid Helium II (0.37). In contrast, mercury at 15C has a surface tension of 487.
thanks for answer but if viscosity in liquids is the result of cohesive forces and if viscosity is zero then cohesive forces are 0. If the cohesive forces are zero will the surface tension be zero or positive?

vanhees71
Science Advisor
Gold Member
Note that zero viscosity means that the fluid particles are very strongly coupled, i.e., the mean free path of the fluid particles is 0. It's the limit of the Boltzmann equation, where the distribution function is always the function of local thermal equilibrium, for which the collision term vanishes identically and entropy is maximal and thus conserved (adiabatic changes of state).

.Scott
Homework Helper
thanks for answer but if viscosity in liquids is the result of cohesive forces and if viscosity is zero then cohesive forces are 0. If the cohesive forces are zero will the surface tension be zero or positive?
Unless the surface is an interface to a vacuum, some consideration needs to be given to the fluid above the surface. Then it becomes a comparison between chemical properties of the super fluid and that of the atmospheric fluid. If the interface IS with a vacuum, then we would need to consider whether that is even a stable interface - or if our super fluid will simply fill the vacuum.