Experimental measurements in a model silo with eccentric hoppers

This study analyses the effect of outlet eccentricity on wall pressures, frictional forces, effective wall friction coefficient, lateral pressure ratio and mass flow rate in a model silo made of corrugated steel and transparent polymethylmethacrylate walls. The silo model consists of two vertical modules (1.5 m in height and a 0.45 × 0.45 square cross section) and a hopper (0.175 m in height and a 0.06 × 0.06 m square outlet). Three different hoppers were used by varying the outlet eccentricity: centred (0 eccentricity), half-eccentric (50 eccentricity), and full-eccentric (100 eccentricity). Pinewood pellets were used as the bulk solid material for the tests conducted. The results indicate that outlet eccentricity causes significant changes in pressure distributions and other parameters. An increase in normal pressure during the discharge was observed on the wall farthest from the outlet (θ = 180°) compared to that measured at the end of the resting phase, while a progressive decrease appears at the wall closest to the outlet (θ = 0°) when increasing hopper eccentricity. Outlet eccentricity also induces an increase of the frictional forces and the weight of the material resting over the hopper at the wall farthest from the outlet, with respect to the wall closest to the outlet. A similar pattern is observed for the lateral pressure ratio. A significantly higher mass flow rate was reported for the full-eccentric hopper with respect to the centred and half-eccentric hoppers.