Study On Meso-mechanism Of Influencing Factors On The Discharge Flow Pattern And Lateral Pressure Of Silo

The force of silo is affected by the geometric and physical properties of the silo and the storage on different level.In this paper,the discrete element method is used to establish different silo models to study the effect of the particle size of the storage material on the discharge pressure and the flow pattern.Based on the distribution of particle velocity,force chain network and lateral pressure during discharge process,the Meso-mechanics is used to reveal the Macroscopic mechanical performance of the storage material.The main research is as follows:(1)Four silo models with different storage diameter were established and the static stored material pressure was output to be compared with the theoretical calculation values.On this basis,the influence of the particle size of the stored material on the discharge pressure was studied by analyzing the changes of the flow pattern of the stored material,the force chain network and the lateral pressure.The results show that the larger the particle size,the greater the discharge pressure peak,which is unfavorable to the stability of the silo structure.During the discharging process,the pressure on the side of the silo wall generally shows a tendency of first increase,then decreases,and the vibration occurs during the increase and decrease.(2)Based on the study(1),for a specific silo model,the movement of granular material has been explored by studying the velocity field and tracking motion locus of representative particles.The force transferring among particles has been discovered by researching the evolution of force chain net.The distribution of granular material has also been learned through studying the evolution of fabric and void ratio.Research results reveals that,the flow pattern is mainly funnel flow for silo with flat bottom and the whole flow area can be divided into linear flow area and dead zone.The profile of emptying pressure onto the silo wall is dynamic,and the peak pressure onto the silo wall happened at discharging ratio of 10 percent.In meso level,particles flowed translational motion throughout discharging.Further study presents that,the study of force chain and motion law of granular material shown the good correspondence between the force chain and the motion state,while heavy force chain means a very low velocity even in station state,the weak force chain means relative high velocity.(3)Based on the study(1),for a specific silo model,the phenomenon that the emptying pressure on silo wall vibrates and increased obviously during discharging is studied based on microcosmic mechanical properties of granular material.Firstly,the effect of arching near the outlet have been proved according to the periodic pressure applied on the bottom wall of a silo during discharging.Then,to study the arching effect,three time points,i.e.start of arching,completion of arching and arch collapse,have been selected.As for each time point,emptying pressure on silo wall,force chain network,vertical stress,lateral stress,the direction of principal stress and velocity field of granular material have been systematically studied.It has been discovered that the arching effect near the outlet behaved dynamically,following the rule of formation and collapse of arch,thus the effect of dynamic arching have been put forwarded.Further,it has been proposed that the increasing emptying pressure on silo wall is caused by the formation of arch,while the vibration of emptying pressure on silo wall is induced by the effect of dynamic arching.