Comment on “Rolling friction in the dynamic simulation of sandpile formation”

The interparticle rolling friction model used by Zhou et al. [1] was adapted from a model for a viscoelastic sphere rolling on a hard plane. We show that the Zhou et al. model is incomplete because it does not predict rolling friction in all cases when rolling friction occurs. Hence, the conclusion drawn by those authors that their numerical results favour an angular velocity independent formulation for rolling friction is premature