Prediction of flow patterns during silo discharges using a finite element approach and its preliminary experimental verification

• An in-house finite element program was used to predict solids flow patterns in silos.
• Upper lateral pressure ratio determined the critical hopper half angle.
• Size and shape of stagnant zone in funnel flow silos were predicted.
• The calculated results showed that placing a double-cone insert could change solid flow patterns.
• Verifications were carried out to check parts of the predicted results using published results.

Obtaining a reliable discharge of particulate solids from a storage silo is a prerequisite to securing operational adequacy in solids handling processes. If a silo is poorly designed, an unreliable interrupted discharge often occurs. In this study, an in-house finite element (FE) program was modified to predict the particulate solids flow patterns during discharges from silos, and the effect of a double-cone insert on such flow patterns. In FE modeling, a Eulerian approach was adopted with an assumption of steady-state flow—a state that greatly facilitated investigations on the effects of double-cone inserts on the flow of particulate solids. Predictions were carried out on whether the discharge was in mass flow or funnel flow, associated with the inclination angle of the silo's hopper. Predicted results were in agreement with the Jenike Chart, and proved that an upper lateral pressure ratio value gave a better critical hopper half angle to achieve mass flow (EN 1991-4, 2006). The shape and size of the stagnant zone were further discussed to address the flow channel boundary between the flowing and static solids if the discharge was in a funnel pattern. Results also showed the effects of a double-cone insert on the flow patterns which converted silos from funnel flow to mass flow up to a certain hopper inclination angle and would improve the flow pattern even for shallower angles. Experiments were carried out to verify some of the predicted results. Some qualitative comparisons were made between the predicted results and experimental measurements, which indicated that further efforts are needed in predicting the shape of the stagnant zone (flow channel boundary) during funnel flow discharges.

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