AN INTERMITTENT ARCH MODEL FOR PREDICTING DYNAMIC PRESSURES DURING DISCHARGE IN GRAIN STORAGE BINS

Arching is a common phenomenon in bulk solids storage structures during discharge. It is hypothesized that dynamic pressures during discharge result from the formation of intermittent arches in grain bins. For free-flowing materials such as agricultural grains, these arches are not strong enough to stop the material flow, but they may slow down the moving material in some locations in the bin. When the moving material is slowed down, an inertia force caused by deceleration will be induced. The arch will also carry some of the material weight above it. Since the arch is supported by the bin wall, both the inertia force and the additional material weight carried by the arch will be transferred through the arch to the bin wall, causing the pressure to increase on the bin wall. Based on this force transfer mechanism, a predictive model was developed for predicting dynamic pressures on the walls of grain bins during discharge. A mass-spring system was proposed to represent the grain bulk in calculating the inertia force caused by deceleration. The predicted dynamic pressure is in good agreement with the experimental data reported in the literature for wheat, and the predicted overpressure factor is in close agreement with that recommended in ASABE Standards for bin design.