Status | Confirmed |
Seminar Series | SEM-PHYS-ENS |
Subjects | cond-mat.soft |
Date | Tuesday 23 January 2018 |
Time | 17:15 |
Institute | DPT-PHYS-ENS |
Seminar Room | room Jean Jaurès (29 rue d'Ulm) |
Speaker's Last Name | Forterre |
Speaker's First Name | Yoel |
Speaker's Email Address | |
Speaker's Institution | Aix-Marseille University |
Title | Stories of grains in fluids: from impact in dense suspensions to micro-avalanches in plant cells |
Abstract | 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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