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Concept
Quantum turbulence
Résumé
Quantum turbulence is the name given to the turbulent flow – the chaotic motion of a fluid at high flow rates – of quantum fluids, such as superfluids. The idea that a form of turbulence might be possible in a superfluid via the quantized vortex lines was first suggested by Richard Feynman. The dynamics of quantum fluids are governed by quantum mechanics, rather than classical physics which govern classical (ordinary) fluids. Some examples of quantum fluids include superfluid helium (4He and Cooper pairs of 3He), Bose–Einstein condensates (BECs), polariton condensates, and nuclear pasta theorized to exist inside neutron stars. Quantum fluids exist at temperatures below the critical temperature at which Bose-Einstein condensation takes place.
The turbulence of quantum fluids has been studied primarily in two quantum fluids: liquid Helium and atomic condensates. Experimental observations have been made in the two stable isotopes of Helium, the common 4He and the rare 3He. The latter isotope has two phases, named the A-phase and the B-phase. The A-phase is strongly anisotropic, and although it has very interesting hydrodynamic properties, turbulence experiments have been performed almost exclusively in the B-phase. Helium liquidizes at a temperature of approximately 4K. At this temperature, the fluid behaves like a classical fluid with extraordinarily small viscosity, referred to as helium I. After further cooling, Helium I undergoes Bose-Einstein condensation into a superfluid, referred to as helium II. The critical temperature for Bose-Einstein condensation of helium is 2.17K (at the saturated vapour pressure), while only approximately a few mK for 3He-B.
Although in atomic condensates there is not as much experimental evidence for turbulence as in Helium, experiments have been performed with rubidium, sodium, caesium, lithium and other elements. The critical temperature for these systems is of the order of micro-Kelvin.
There are two fundamental properties of quantum fluids that distinguish them from classical fluids: superfluidity and quantized circulation.
Source officielle
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