Propagation of internal deformations in dense granular flows

This paper analyses how local deformation develops in dense granular flows. Local kinematic fields including particle velocity fluctuations, local strain, and non-affine deformation are measured in simulated homogeneous shear flows at different inertial numbers I, prescribing the shear strain rate  and the normal stress. Results evidence that these fields are unsteady and spatially correlated, as previously observed in a wide range of soft materials. They reveal a mechanism of propagation of local deformation by which seed events of particle rearrangements trigger further rearrangements in their vicinity. It appears that this mechanism is strongly dependent on the inertial number, with cluster size and propagation velocity increasing as a power law of I when I → 0. This mechanism can help understand and model some behaviours of granular flows such as non-locality and transient rheology.