Vendredi 31 mai à 11h00, salle des séminaires IRPHE
Abstract : When a granular material flows around an intruder, it generates a velocity field and forces related to the specific rheology of the granular medium . In this presentation, we will consider two situations involving granular flows around intruders and the resulting forces. 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, w e study the decrease in granular flow rate due to the presence of pillars. These observations are rationalised by a model that takes into account the forces applied by the pillars on the granular layer. The second situation concerns the interaction between a pair of spherical intruders moving side-by-side into grains at constant depth and speed . We observe a cooperative effect between the spheres, as the mean drag force on one sphere is lower at small separation distances than at large separations. Finally, we will briefly discuss how an understanding of the interaction between objects and grains can be used to approach the problem of animal locomotion in granular environments.