  We carry out a detailed comparison of soft particle molecular dynamics
simulations with the theory of partially fluidized shear granular flows. We
verify by direct simulations a constitutive relation based on the separation of
the shear stress tensor into a fluid part proportional to the strain rate
tensor, and a remaining solid part. The ratio of these two components is
determined by the order parameter. Based on results of the simulations we
construct the ``free energy'' function for the order parameter. We also present
the simulations of the stationary deep 2D granular flows driven by an upper
wall and compare it with the continuum theory.
