Energy cascade mechanisms in turbulent superfluid helium
| When |
May 21, 2026
from 11:00 to 12:00 |
|---|---|
| Where | MGN1 105 |
| Attendees |
Juan Ignacio Polanco |
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Near absolute zero, helium-4 is present in a superfluid state where it displays unique hydrodynamical properties. Besides the absence of viscosity in the zero temperature limit, all rotational degrees of freedom of the fluid are concentrated on quantum vortices of atomic-size thickness whose circulation is quantised. Despite these striking differences with classical viscous fluids, turbulence in superfluids has been shown to display significant similarities with classical fluid turbulence, including the emergence of Kolmogorov scaling laws and intermittency. This is expected in particular at scales larger than the quantum scale associated to the typical distance between quantum vortices, of the order of tens of microns in typical experiments, and where collective vortex dynamics can be expected to dominate. In this talk, I will argue that the picture is more complicated than that due to the very wide extent of the smaller scales, between the quantum scale and the atomic core size, which are typically separated by several orders of magnitude. Using simple theoretical arguments and unprecedented numerical simulations, I will show that these scales can act as an energy sink in turbulent superfluids, receiving energy directly from the turbulent large scales via a mechanism analogous to vortex stretching in classical flows. Crucially, such energy transfers bypass the scale-local energy cascade usually associated to Kolmogorov's turbulence phenomenology, and thus result in non-classical scaling laws above the quantum scale. I will finally discuss the potential significance of this mechanism in finite temperature regimes more relevant to experiments, where quantum vortices coexist and interact with a viscous normal fluid.