Events

Abstract : Quantum fluids exhibit peculiar features such as a two-fluid nature, inviscid flow and quantised
vorticity. Despite these non-classical dynamical properties, turbulent flows in quantum fluids may
show surprising classical features in terms of energy spectra, energy decay and one-point statistics
as, for instance, the statistical distribution (PDFs) of velocity and acceleration components.
The observation of classical or exclusively quantum flow characteristics is strongly related
to the interaction of quantised vortices with Landau’s sea of thermal excitations [1]: the so-called
mutual friction force between quantised vortices and the thermal component can either couple
(lock) the latter producing quasi-classical features or generate inevitably dissipative flow structures
akin to wakes which have no classical analog.
In this seminar I will report numerical evidence in superfluid He4 flows showing both the
observation of classical-like behaviours in the propagation of macroscopic quantum vortex bundles
[2] and the emergence of non-classical statistics in thermally driven flows [2]. Our results, in
addition to illustrating the peculiarities of turbulent flows in superfluid He4 , also provide useful
hints for the interpretation of past and future experimental measurements performed employing
solid hydrogen tracking particles in Institut Néel and Charles University in Prague [4,5,6].

[1] Landau, L.D. , Theory of the superfluidity of helium II. J. Phys U.S.S.R. 5, 71 (1941)
[2] Galantucci, L, Krstulovic, G and Barenghi, CF, Friction-enhanced lifetime of bundled quantum
vortices. Phys Rev Fluids 8, 014702 (2023)
[3] Galantucci, L, Krstulovic, G and Barenghi, CF, Quantum vortices leave a macroscopic signature
in the thermal background, arXiv:2501.08309 (2025)
[4] P. Švančara, D. Duda, P. Hrubcová, M. Rotter, L. Skrbek, M. La Mantia, E. Durozoy, P.
Diribarne, B. Rousset, M. Bourgoin, et al., J. Fluid Mech. 911, A8 (2021)
[5] P. Švančara and M. La Mantia, Coherent propagation of vortex rings at extremely high Reynolds
numbers, J. Fluid Mech. 953, A28 (2022)
[6] Peretti, C, Vessaire, J, Émeric D and Gibert, M., Direct visualization of the quantum vortex
lattice structure, oscillations, and destabilization in rotating He4, Science Advances 9 (30),
eadh2899