Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Domaines cond-mat.soft
Date Mardi 23 Janvier 2018
Heure 17:15
Salle room Jean Jaurès (29 rue d'Ulm)
Nom de l'orateur Forterre
Prenom de l'orateur Yoel
Addresse email de l'orateur
Institution de l'orateur Aix-Marseille University
Titre Stories of grains in fluids: from impact in dense suspensions to micro-avalanches in plant cells
Résumé Over the past twenty years, great progress has been made in our understanding of how granular matter flows, a topic of both basic and practical interest. A distinctive feature of granular flows is that they display a flow threshold and a maximal packing fraction, beyond which no permanent flow is possible (jamming transition). In this seminar, I will illustrate how physical phenomena at the particle level (fluid drag, colloidal forces, particle agitation) can profoundly affect the flow behavior of a mixture of grains and fluids close to the jamming transition. First, I will show that the short-time response of a dense suspension under impact is entirely controlled by the coupling between transient effects (Reynolds dilatancy) and the fluid pressure. I will then discuss how the addition of short-range repulsive forces between grains can conspire with friction to yield the dramatic shear-thickening behavior displayed by some suspensions like cornstarch. Finally, I will show how the sensor of gravity of plants relies on intracellular micro-avalanches flowing in an active liquid.
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