Why does zero viscosity allow superfluids to climb?

In summary, the mechanism that drives superfluidity to climb up the sides of a container is gravity. The superfluid, being less dense than the surrounding fluid, will climb the walls due to the pressure from the layers above and its own gravitational potential. This is similar to the phenomenon of ferromagnetism. However, perpetual motion using superfluids is not possible due to the energy required to maintain the low temperature and extract energy from the system. Additionally, in a free fall lift, no climbing will occur due to the absence of gravity.
  • #1
Chronothread
51
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Since there are no frictional forces acting on the superfluid my intuition would tell me that there is no way for the liquid to "climb" the sides of a container. Obviously though, intuition isn't the best thing to go by when it comes to superfluids. I'm just wondering: what mechanism drives it to climb up when there's no fluid there in the first place?

A slightly different question and one that is always met (and for good reason) with large amounts of skepticism, is perpetual motion. I was reading about superfluids and came across the idea that if you had a superfluid spinning in a container it would spin indefinitely. Is this kind of perpetual motion possible other then the fact that you have to keep the substance at a very low temperature?
 
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  • #2
What makes you think there's no fluid on the sides of the container?

As far as your second question, do you know what perpetual motion machine is? It's not something moving perpetually; it's extracting energy from a closed system.
 
  • #3
I had heard that if the container was not sealed the superfluid would move into a lower container. So I figured that meant it must not require there to be the substance on the sides of the container in the first place allowing it to climb up. However, I may have just heard wrong or where I heard it from might have not been saying it exactly as is scientifically true. Does it require small amounts of the superfluids to be there in the first place?

As for the definition of perpetual motion, as far as I've seen it's just a device that will continue to operate without the introduction of energy from an external force. Most likely though you know more about it then I do. But it's true that the superfluid would keep spinning forever right? Or is there some other mechanism that would stop it?
 
  • #4
There are small amounts of superfluid on the edge. You have evaporation and you have condensation, right? Hence my question - why do you think there's no fluid on the sides of the container?
 
  • #5
There is no resistance to flow (zero viscosity). The fluid must be less dense than the surrounding fluid for it to climb the walls (Archimedes).
 
  • #6
Chronothread said:
As for the definition of perpetual motion, as far as I've seen it's just a device that will continue to operate without the introduction of energy from an external force. Most likely though you know more about it then I do. But it's true that the superfluid would keep spinning forever right? Or is there some other mechanism that would stop it?

Keep in mind several things:

- The energy reguired to lower a temperature to that degree.
- The energy required to keep a superfluid at that temperature during physical energy extraction.

So, is it possible to extract energy from the superfluid phenomenon itself? Yes! Of course!

Does the possible energy extracted equal or exceed the energy required to allow the superfluid phenomenon to occur and maintain itself? No.
 
  • #7
The superfluidity is analogues to ferromagnitism. It is more favorable (energetically) to get to motion in some direction, than to be calm (V=0).

So it is the answer :)
 
  • #8
The mechanism of climbing fluidity is in fact very simple: the gravity. Suppose some Helium superfluid is held in a glass. Now it has a finite liquid column height, which means a gravitational potential. Now let's imagine the column is as stacked from thin layers, upper ones pressing lower ones due to gravity. Therefore, the bottom layer shall be pushed and will climb along the cup wall to escape the pressure if no friction exists. That is why superfluidity climbs. It does so and its potential energy lowers.

The above idea can be easily tested by holding a cup of Helium in a free fall lift. No climbing should happen in this case.
 
  • #9
hiyok said:
The mechanism of climbing fluidity is in fact very simple: the gravity. Suppose some Helium superfluid is held in a glass. Now it has a finite liquid column height, which means a gravitational potential. Now let's imagine the column is as stacked from thin layers, upper ones pressing lower ones due to gravity. Therefore, the bottom layer shall be pushed and will climb along the cup wall to escape the pressure if no friction exists. That is why superfluidity climbs. It does so and its potential energy lowers.

Um...potential energy is still mgh, no?

If you look at a container of superfluid helium (not so easy - there is fog and frost seemingly everywhere) you will see that the fluid layer covers the outside as well, so you end up essentially with a siphon. The helium flows up initially but eventually ends up lower.
 
  • #10
What I want to emphasize is that, the force driving the climbing is the gravity, while potential energy lowering is a consequence.
 

1. Why does zero viscosity allow superfluids to climb?

Zero viscosity, or the complete absence of resistance to flow, is a property of superfluids that allows them to climb. This is because without viscosity, there is no dissipation of kinetic energy as the fluid moves. This results in a continuous circulation of the fluid, allowing it to overcome the force of gravity and climb up walls or containers.

2. What is the significance of superfluids climbing?

The ability of superfluids to climb has many practical applications, such as in cryogenics and refrigeration systems. It also has important implications in understanding the behavior of matter at extremely low temperatures and in the study of quantum mechanics.

3. How does zero viscosity affect the behavior of superfluids?

In addition to allowing superfluids to climb, zero viscosity also leads to other unique properties such as infinite thermal conductivity and the ability to flow without turbulence. These properties are a result of the fluid's ability to maintain a constant velocity without any loss of energy.

4. What are some real-life examples of superfluids climbing?

One well-known example is the "fountain effect" seen in liquid helium at temperatures close to absolute zero. The liquid can climb out of a vessel and form a fountain-like shape due to its zero viscosity. Another example is the "levitation effect" where a superfluid can flow up and over an obstacle without any loss of energy.

5. Can any fluid exhibit zero viscosity and climb?

No, only certain fluids that have undergone a phase transition at extremely low temperatures can exhibit the properties of zero viscosity and climbing. Examples of these fluids include liquid helium, atomic Bose-Einstein condensates, and neutron stars.

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