Flow pattern and normal pressure distribution in flat bottom silo discharged using wall outlet

Abstract

Flow patterns and normal wall pressures in a flat bottom silo discharged from a wall outlet were investigated through experiment and discrete element method. The fine sand was used to study the flow pattern while glass beads to study both the flow pattern and the distribution of normal wall pressure. Effects of wall outlet dimensions and shapes on the flow pattern and normal wall pressure were also presented. During the discharge, the bulk material in the silo was divided into three zones, which were the static zone, the pressure ear zone and the flow funnel. Normal wall pressures in the static zone and the pressure ear zone during discharge were much greater than that in the static state. The discharge overpressure factor was about 1.64 in the static zone, and had value of over than 2.0 in the zone of pressure ear. And the normal pressure in the flow funnel zone during discharge could be lower than that in the static state. Discrete element simulations on a silo storing glass beads were carried out to study the flow pattern and the distribution of normal wall pressure. The flow patterns in discrete element simulation agreed well with the test results while the normal wall pressures were about 5% higher than the test results. At the same time, the flow pattern inside the bulk material and the formation of flow channel in the discrete element model was presented by slicing the model apart, which could not be observed in the model test.