PFC Numerical Simulation Of Silo Unloading Pressure Considering The Influence Of Silo Diameter

When the silo is unloaded,the dynamic pressure of the bulk material on the wall of the silo is much than the static pressure.Up to now,there is no widely accepted reasonable theory to accurately predict the dynamic pressure.The former silo test and numerical simulation mostly used the reduced model silo to carry on the research,compared with the grain silo of tens of meters high,probably will have the certain error.Based on the silo unloading experiment,the silo numerical model was established to simulate the unloading process.Obtaining the dynamic pressure and distribution.The difference of silo pressure with different size numerical models was explored.The flow state during discharging process was observed and the relationship between flow state change and dynamic pressure was analyzed.Some of the following have been done:(1)The unloading test was carried out in a glass silo with a height 5.5 m and an inner diameter of 1.5 m.The static lateral pressure and dynamic pressure were obtained and the grain flow state during unloading was observed.It is found that the maximum dynamic pressure appears at the initial stage of unloading,which is more than twice as high as the static pressure.(2)The PFC2 D silo model was established on the basis of the experiment,and the mechanical parameters of the model were determined.The static and dynamic pressure and the change of particle unloading flow form were obtained by the simulating process and compared with the test.It is found that the maximum dynamic pressure of numerical simulation is basically consistent with the experimental value,and the variation trend is very consistent,which indicates that the dynamic pressure of silo can be predicted by numerical simulation.(3)In order to study the influence of silos’ model size on pressure,two original scale models were established.The static and dynamic pressures were obtained respectively.It is found that the dynamic pressure of the scale model is not different from that of the original warehouse,and the pressure of reducing the size by3 times increases by 1 / 10.It shows that it is feasible to obtain the pressure of large silos by the model of scale silos.(4)The change of particle velocity field and contact force during the numerical simulation of silo unloading was observed and compared with the test.It can be seen that the whole flow of the material occurs in the first half of the discharge period.When the material is about 1 / 3 of the remaining material,it gradually becomes a tubular flow form.