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Accueil > Actualités > Séminaires > Séminaires 2022

Jeudi 31 Mars 11h00 - LEGI Salle K118

Sofía Angriman, University of Buenos Aires

Title : Mirror, mirror on the wall : helicity and the knottedness of tracers’ trajectories in turbulence.

Contact : Martin Obligado

Abstract : When particles move in a turbulent flow, their trajectories cross each other. When looking through a mirror, the particles would still cross, but the linkage of their paths would be able to tell the mirror version from the real one. The more knotted the flow is, the more the paths of the particles intertwine : the linkage of these trajectories is sensitive to the flow helicity, a magnitude that quantifies the topological complexity of the flow.

By combining data from simulations of helical homogeneous and isotropic turbulence and Taylor-Green flows, with laboratory experiments of mirror-symmetric HIT and of chiral von Kármán flows, and analyzing Lagrangian particles’ trajectories, we find that the linkage of the curves holds information on the structure of the underlying flow in which the particles move. And conversely, the knottedness of the turbulent flow has a quantifiable effect on the way particles mix. This relationship allows estimating the mean, global helicity of a flow directly from counting the crossings of tracers’ trajectories, a measurement which so far has eluded detailed experimental characterization.