Erosion and spreading of granular material

SVI Lab, CNRS & Saint Gobain - UMR 125

Granular media constitute a complex material that can rest like a solid, flow like a liquid but also interact with a surrounding fluid. In this talk, I discuss two recent studies devoted to direct or indirect shaping of a granular medium. We first consider the spreading of a granular media with a blade, a situation encountered in applications that range from the bulldozing of snow to coating processes. We rely here on a model experiment to characterize the three-dimensional spreading on a flat surface and we rationalize the deposited pattern through the granular flow in the bulldozed dune. The second situation involves the erosion of a granular bed by a fluid flow. Indeed, some bottom-dwelling fish, such as the flounders, generate a flow capable of resuspending sand, to avoid predators. By flapping their fins, they create vortices that lifts the sand particles up and deposits them on top of their backs. A model experiment has been developed to study this situation and characterize the onset of the erosion of the granular bed.