  This paper establishes a link between the non-local behaviour of granular
materials and the presence of transient clusters of jammed particles within the
flow. These clusters are first evidenced in simulated dense granular flows
subjected to plane shear, and are found to originate from a mechanism of
multiple orthogonal shear banding. A continuum non-local model, similar in form
to the non-local Cooperative model, is then derived by considering the spatial
redistribution of vorticity induced by these clusters. The non-locality length
scale is thus expressed in terms of the cluster size. The purely kinematic
nature of this derivation indicates that non-local behaviour should be expected
in all glassy materials, regardless of their local constitutive law, as long as
they partially jam during flow.

Soft Condensed Matter