Quantum turbulence in flows of superfluid 4He

Abstract: I will review the essential results achieved in three years of activities at the Joint Low Temperature Laboratory on the study of turbulent superfluid flows. Superfluid turbulence is conceptually simpler than turbulence in classical fluids because at small scales it is constituted by identical discrete vortices with quantized and conserved velocity circulation, but at large scales can have a behavior very similar to classical fluids. It therefore represents an opportunity both for studying fundamental quantum mechanical effects on macroscopic systems, and for an alternative approach to the important open problem of classical turbulence. I will describe experiments where a turbulent flow of superfluid 4He has been generated with a low temperature bellows which injects helium into flow channels. The turbulence is detected by measuring the attenuation of second sound propagating across the turbulent medium. The onset conditions, the sustained steady state and the decay of turbulence have been studied. The results will be examined in historical context and within the current debate.