We use existing 3D Discrete Element simulations of simple shear flows ofspheres to evaluate the radial distribution function at contact that enableskinetic theory to correctly predict the pressure and the shear stress, fordifferent values of the collisional coefficient of restitution. Then, weperform 3D Discrete Element simulations of plane flows of frictionless,inelastic spheres, sheared between walls made bumpy by gluing particles in aregular array, at fixed average volume fraction and distance between the walls.The results of the numerical simulations are used to derive boundary conditionsappropriated in the cases of large and small bumpiness. Those boundaryconditions are, then, employed to numerically integrate the differentialequations of Extended Kinetic Theory, where the breaking of the molecular chaosassumption at volume fraction larger than 0.49 is taken into account in theexpression of the dissipation rate. We show that the Extended Kinetic Theory isin very good agreement with the numerical simulations, even for coefficients ofrestitution as low as 0.50. When the bumpiness is increased, we observe thatsome 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 flowsresemble simple shear flows, i.e., flows of rather constant volume fraction andgranular temperature.
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