Rheology of Granular Materials and Sound Emission near the Jamming Transition

It is supposed that the shear stress of non cohesive granular material in the vicinity of the jamming transition is connected to the formation of transient rigid clusters of particles. Their characteristics are investigated as a function of the imposed pressure, the solid volume fraction and the shear rate. Those clusters are responsible for an increase of the shear stress for a vanishing shear rate, which leads to an instability close to the jamming transition. We debate the consequences for stick‐slip motion and flows down an inclined plane, in agreement with the observations. The oscillation of the granular material between two flow states generates fast velocity fluctuations. We infer that under certain conditions regarding the particles and the average flow height, an intermittent regime near the jamming transition, at a well defined frequency, can be a source of sound emission.