Numerical Simulation of Dynamic Lateral Pressure during Vertical Silo Unloading Based on the Discrete Element Method
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Abstract:
The dynamic lateral pressure when unloading vertical grain silos can render the process unsafe; thus, three types of grains (corn, wheat, and rice) were selected to simulate unloading using the discrete element simulation software, EDEM. The static lateral pressure distribution under the physical characteristics and contact properties of different stored materials was studied and compared with the specification value. The distribution patterns of dynamic lateral pressure and the corresponding overpressure coefficient, flow state, and velocity distribution relationships during unloading were analyzed together with the factors influencing the dynamic lateral pressure during unloading using gray relational analysis. The results showed that the maximum static lateral pressure for all three types of stored materials occurs towards the bottom of the silo wall and is greater than the specification value. Hence, the value calculated using the specification formula can be considered relatively conservative. Increased oscillation of the dynamic lateral pressure during unloading and the maximum dynamic lateral pressures of 6.08, 5.38, and 4.73 kPa observed for corn, wheat, and rice, respectively, at a depth of 0.8 m exceeds the correction coefficient for horizontal lateral pressure required in the specifications. Thus, the correction coefficient for horizontal lateral pressure required by the current code is unsafe. The main factors affecting the dynamic lateral pressure include the density of the stored material, the static friction coefficient between the stored material and the silo wall, and the collision recovery coefficient between the stored material and the silo structure. This paper can provide theoretical support for the analysis of the collision recovery coefficient between stored materials and silo structures for use in silo specifications.
