Experimental Developments
Superfluidity is only observed "naturally" in two liquids: helium-4 and the rarer isotope, helium-3. Quantum turbulence was first discovered in pure 4He in a counterflow (where the normal and superfluid components are made to flow in opposite directions) generated by a steady heat current. See superfluid helium-4. Since the two-fluid model, and therefore counterflow itself, is unique to superfluids, this counterflow turbulence is not observed classically; the first observations of turbulence with direct classical counterparts has come much more recently through the investigation of pressure fluctuations in rotational flow and grid turbulence.
In 3He-4He mixtures, like in dilution refrigerators, quantum turbulence can be created far below 1 K if the velocities exceed certain critical values. For velocities above the critical velocity there is a dissipative interaction between the superfluid component and the 3He which is called mutual friction.
Read more about this topic: Quantum Turbulence
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