Bulletin of the American Physical Society
75th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 20–22, 2022; Indiana Convention Center, Indianapolis, Indiana.
Session A03: Active Matter I: Active Turbulence
8:00 AM–9:57 AM,
Sunday, November 20, 2022
Chair: Paulo Arratia, UPenn
Abstract: A03.00003 : Friction-enhanced lifetime of bundled quantum vortices
8:26 AM–8:39 AM
(Observatoire de la Cote d'Azur, CNRS Laboratoire Lagrange, Universite' de la Cote d'Azur)
directly, but also indirectly by changing the common background. A typical example
of this interplay is hydrodynamic cooperation characterising systems of active agents
such as aqueous suspensions of self-propelled bacteria, fungal spores dispersed in air, road
racing cyclists in pelotons and particle pairs trapped in optical vortices; in these systems
self-organized structures emerge from collective energy-saving mechanisms.
Here we report a similar collective effect existing in superfluid helium at finite temperatures.
By performing cutting-edge numerical simulations of superfluid helium dynamics, we show
that a toroidal bundle of quantized vortex rings generates a large-scale wake
in the normal fluid which reduces the overall friction experienced by the bundle, thus
greatly enhancing its lifetime, as observed in experiments.
This remarkable collective effect - the reduction of dissipation via
hydrodynamic cooperation - displays similar features than the ones observed in particle drafting in optical
vortices. Superfluid helium can hence be considered as a peculiar kind of active fluid,
where hydrodynamic interactions determine the characteristics of turbulence in both superfluid and normal fluid components.
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