Interplay between hydrodynamics and non-passive particles
Orateur : Severine Atis, Harvard University
Abstract : The dynamics of non-passive particles or living organisms in fluid flows can be considerably different from infinitesimal fluid particles, leading to distinct clustering and dispersion phenomena. From pollutant transport and plankton distribution on the ocean surface, to accretion phenomena in astrophysics, predicting the dynamics of finite-sized objects in a given field of force matters in a wide variety of natural phenomena and industrial processes. In this talk, I will present two laboratory experiments combined with numerical modeling where the coupling between hydrodynamics and non-passive particle’s properties leads to emergent dynamics. I will first describe the effect of particle’s shape on their dispersion in complex flows. Neutrally buoyant particles with an anisotropic shape can respond to fluid flows very markedly from isotropic ones, leading to a variety of phenomena such as orientation dependent dynamics, chaotic trajectories, or periodic motions. Here I will focus on rod-shape particles and show that they can exhibit distinct preferential concentration regions in the flow field, and present a simple model to describe this behavior. I will then present the interplay between fluid flows and "active particles" in the context of an expanding population of microorganisms. The metabolic activity of the colony generates a flow which in turn accelerates the cells propagation on the liquid interface. This coupled system can lead to the formation of a variety of morphologies including the formation of jets of dividing cells at the colony edge, or the complete fragmentation of the initial colony.
Date et lieu : jeudi 19 décembre 2019 à 11h dans la salle de séminaire IRPHE
Voir en ligne : la page personnelle de l’orateur