  We use existing 3D Discrete Element simulations of simple shear flows of
spheres to evaluate the radial distribution function at contact that enables
kinetic theory to correctly predict the pressure and the shear stress, for
different values of the collisional coefficient of restitution. Then, we
perform 3D Discrete Element simulations of plane flows of frictionless,
inelastic spheres, sheared between walls made bumpy by gluing particles in a
regular array, at fixed average volume fraction and distance between the walls.
The results of the numerical simulations are used to derive boundary conditions
appropriated in the cases of large and small bumpiness. Those boundary
conditions are, then, employed to numerically integrate the differential
equations of Extended Kinetic Theory, where the breaking of the molecular chaos
assumption at volume fraction larger than 0.49 is taken into account in the
expression of the dissipation rate. We show that the Extended Kinetic Theory is
in very good agreement with the numerical simulations, even for coefficients of
restitution as low as 0.50. When the bumpiness is increased, we observe that
some of the flowing particles are stuck in the gaps between the wall spheres.
As a consequence, the walls are more dissipative than expected, and the flows
resemble simple shear flows, i.e., flows of rather constant volume fraction and
granular temperature.
