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The defence will be in English.
Abstract: Quantum vortices are a core element of superfluid dynamics and elusively hold the keys to our understanding of energy dissipation in these systems. In this thesis, we introduce the HeII phase with most of its peculiar properties, and we present a brief description of the CryoLEM, an rotating cryostat that we used to explore this phase of 4He. We show that we are able to visualise these vortices in the canonical and higher-symmetry case of a stationary rotating HeIIbucket. Using direct visualisation, we quantitatively verify Feynman’s rule linking the resulting quantum vortex density to the imposed rotational speed. We make the most of this stable configuration by using it as a reproducible initial condition to probe HeII under a rotating counterflow regime, by applying an alternative or constant heat flux aligned with the axis of rotation. Moderate amplitudes led to the observation of collective wave mode propagating along the vortices, and high amplitudes led to quantum vortex interactions. The waves were quantitatively observed using Particle Tracking Velocimetry and Particle Imaging Velocimetry techniques, leading to a first visual endeavour into the waves propagating along quantum vortices through the lens of their dispersion relation. When increasing the heat flux, we obtained quantum vortex interactions, of which we studied the boundaries of the regime. The observed quantum vortex reconnections led the system to an onset of turbulence under steady rotation, therefore this ensemble of regimes defines a path toward quantum turbulence in rotating HeII and sets a baseline to consolidate the descriptions of all quantum fluids. Furthermore, the Gross-Pitaevskii numerical study of the particle shape influence on their trapping on quantum vortex core is undertaken, showing that it indeed holds an influence on the Magnus frequency of the trapping. Alongside it, qualitative numerical simulations on accelerated non-spherical particles are undertaken, showcasing the possibilities of the updated FROST code.
