  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.
