障碍物对容器出口处颗粒物堵塞概率影响分析

Analysis of the Influence of Obstacle on the Clogging Probability of Particle Blockage at the Outlet of Container

容器出口处的堵塞是颗粒物质研究中的一个热点和难点问题。实验证实,如果在容器出口处放置障碍物,会大幅度降低颗粒物堵塞概率,但其背后物理机理仍旧不清晰。通过实验获得颗粒物压力等信息较为困难,本文利用离散元软件研究障碍物中心距离出口高度及其几何尺寸对平底筒仓堵塞概率的影响。模拟结果表明当障碍物中心距离出口高度取出口尺寸的两倍时,能明显降低堵塞概率,随着高度升高,堵塞概率趋近于无障碍物时的大小,而障碍物尺寸对堵塞概率无明显影响。为研究该问题的背后物理因素,求解了不同障碍物中心距离出口高度下出口处颗粒物体积分数、竖直方向速度以及接触压强的平均值,结果表明,出口处接触压强是影响堵塞概率的首要因素。该研究将为高温气冷堆出口处设计以及门后立柱等交通流问题提供理论依据。

Clogging phenomenon is one of the most fundamental subjects in the research of granular media which has attracted significant attention.It has been shown experimentally that the presence of an obstacle above the orifice can significantly reduce the clogging probability of particles discharging from a silo.However,the underlying physical mechanism still remains unclear.As it is difficult to obtain the information of contact pressure from experiment,in this work,we study the effect of the obstacle position and size on the clogging phenomenon of a flat-bottomed silo by using discrete particle simulation.The simulation shows that when the distance between the obstacle center and bottom of the silo is twice the orifice size,the clogging probability can be significantly reduced.As the obstacle position value increases,the clogging probability approaches the value obtained in the case without obstacle.The size of the obstacle has no significant effect on the clogging probability.To understand the underlying physical mechanism,we calculate the following parameters:the statistical averaging of the volume fraction,vertical velocity and contact pressure of particles near the aperture during discharge.We find that,among all relevant variables,the contact pressure of particles is the main cause of the variation of clogging probability.This study provides a theoretical basis for the design of the exit of the high-temperature gas-cooled reactor and for the research on traffic flow problems such as the column behind the door.