  We study the rheological properties of a granular suspension subject to
constant shear stress by constant volume molecular dynamics simulations. We
derive the system `flow diagram' in the volume fraction/stress plane
$(\phi,F)$: at low $\phi$ the flow is disordered, with the viscosity obeying a
Bagnold-like scaling only at small $F$ and diverging as the jamming point is
approached; if the shear stress is strong enough, at higher $\phi$ an ordered
flow regime is found, the order/disorder transition being marked by a sharp
drop of the viscosity. A broad jamming region is also observed where, in
analogy with the glassy region of thermal systems, slow dynamics followed by
kinetic arrest occurs when the ordering transition is prevented.

Soft Condensed Matter;Statistical Mechanics