LPS, amphi moyen


12 May 2023


11h00 - 12h00

Granular flows around intruders, Baptiste Darbois-Texier (FAST, Université Paris-Saclay)

When a granular material flows around an intruder, it generates a velocity field and forces in relation with the rheology of the granular medium. In this presentation, we will consider two situations involving granular flows around intruders and where we consider the forces acting on them. The first situation concerns the flow of a granular layer along a slope covered by a forest of pillars. This configuration is inspired by the role of tree forests in mitigating mountain avalanches. Using a small-scale experiment, we study the decrease in granular flow rate due to the presence of the pillars and develop a theoretical model that takes into account the forces applied by the pillars on the granular layer. The second situation concerns the penetration of a cylinder in a granular medium by successive impacts. This problem arises in particular with space probes used for the underground exploration of sandy planets. In this experiment, we observe two different intrusion regimes for a small and a large number of impacts, which can be rationalized by considering the granular forces acting on the cylinder. Finally, we will briefly discuss the interest of studying the interaction between a moving object and a granular medium in relation to our current research on animal locomotion in granular environments.