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3-part question, but I think it's simple enough...

  1. Does the tendency for cavitation in a fluid depend on its viscosity?
  2. If so what does this imply for superfluids, having 0 viscosity?
  3. And for that matter can bubbles even form due to cavitation in a superfluid (without breaking the superfluid state)?

Note re #3 - I am aware that the physical state must change for bubbles to form. What I am interested in is whether superfluids allow bubbles to form without destroying the state for the rest of the superfluid. That is, would a bubble (or I suppose impurity in the general) in a superfluid prevent superfluidity nearby, either as the result of the process that formed the bubble or from the presence of the bubble itself?

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Cavitation inception occurs when the local pressure is less than the vapour pressure of the liquid. In effect the liquid locally boils to form a bubble of vapour.

But producing the pressure gradients required to boil the liquid require a non-zero stress, or more precisely the viscous stress tensor has to be non-zero. In a superfluid the stress is always zero because the stress is the viscosity multiplied by the strain rate. Since the viscosity is zero that means means the viscous stress tensor is also always zero.

So cavitation cannot happen in a superfluid.

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Answering on the third part of your question bubbles rely on the temporary breaking of a fluid state, so it would not be possible

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  • $\begingroup$ fair point. edited to reflect the aim of the question better $\endgroup$ – Xeren Narcy Jul 21 '15 at 5:41

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