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Quantum turbulence

If one cools any gas sufficiently it will become a liquid, and with sufficient pressure will become a solid. Helium can also become a superfluid if the temperature is sufficiently low and the pressures are not very high. What is a superfluid? It is a quantum state with zero viscosity whose underlying equation is a quantum nonlinear Schrodinger equation, not the Navier-Stokes or Euler equations. A state similar to that in a resistance-free superconductor. That is, at least a low velocities, a superfluid will flow without resistance. So why would engineers be interested in this bizarre medium? Because despite being inviscid, once the velocity exceeds a threshold, a superfluid resists flow in exactly same way as a classical turbulent fluid obeying the viscous Navier-Stokes equations. Why? Just as we don’t know exactly why a classical laminar fluid becomes turbulent, we don’t know why a superfluid becomes turbulent. But in both cases, vortices seem to be the key and in the quantum case these are easier to model than classical vortices. So if we understand the quantum case, it could, and has, give us clues for the origin of classical turbulence.