The surprising relevance of a continuum description to granular clusters

Nature shuns homogeneity. In turbulent clouds, industrial reactors and geophysical flows, discrete particles arrange in clusters, posing difficult challenges to theory. A persistent question is whether clusters can be modelled with continuum equations. Recent evidence presented by Mitrano et al. (J. Fluid Mech., vol. 738, 2014, R2) indicates that suitable equations can predict the formation of clusters in granular flows, despite violating the simplifying assumptions upon which they are based.