Eulerian vs Lagrangian Irreversibility in an experimental turbulent swirling flow
Résumé
In a turbulent fluid, the time-reversal symmetry is explicitly broken by viscosity, and spontaneously broken in the inviscid limit. Recently, Drivas proved the equivalence of two different local indicators of time-irreversibility: i) an Eulerian one, based on regularity properties of the velocity field ii) a Lagrangian one, based on symmetry properties of the trajectories under time reversal. We test this equivalence in a turbulent Von Kármán experiment at a resolution of the order of the Kolmogorov scale using a high resolution 4D-PTV technique. We use the equivalence to perform the first joined Eulerian-Lagrangian exploration of the dynamics leading to time irreversibility, and find that it is linked with vortex interaction, suggesting a link between irreversibility and singularity.
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