The present work investigates hopper discharge phenomenon from a quasi-3D, rectangular hopper using the Discrete Element Method. Accurate prediction of the discharge rate from hoppers is important in many industrial processes involving the handling of granular materials. For cohesionless granular media, the effects of particle properties (particle size and size distribution) and hopper geometry (hopper width, outlet width, angle and fill height) are studied and compared to previously published experimental correlations. The results indicate that DEM simulations are fully capable of reproducing trends in the discharge rate that are well-known experimentally. For example, particle size and hopper width are shown to have a minimal influence on the discharge rate. In addition, for rectangular hoppers, the discharge rate is shown to vary with the outlet width raised to the 3/2 power as given by the modified Beverloo correlation. The DEM simulations are also used to explore a wider range of parameters that have not been or are not easily explored experimentally. For example, the effects of hopper friction, particle friction, and coefficient of restitution are investigated, and particle friction is shown to have a significant influence on the hopper discharge behavior.;The present work also investigates the parameters affecting the discharge rate of a wet cohesive system. The cohesion between the particles is described by a pendular liquid bridge force model and the strength of the cohesive bond is characterized by a Bond number. The Beverloo correlation is applied to cohesive systems by modifying the Beverloo constant as a function of Bond number. The predictions obtained from this modified correlation fit the simulation data reasonably well. In addition, the effect of hopper angle in cohesive systems is shown to follow a trend similar to cohesionless systems, where the discharge rate is insensitive to changes in hopper angle except below a critical angle (with respect to the vertical) where the discharge rate increases rapidly. This critical angle of flow decreases with increasing cohesion.;Granular materials may readily segregate due to differences in particle properties such as size, shape, and density. Segregation is common in industrial processes involving granular materials and can occur even after a material has been uniformly blended. One of the specific objectives of this work includes investigating via simulation the effect of particle cohesion due to liquid bridging on particle segregation. Specifically, a bi-disperse granular material flowing from a 3-D hopper is simulated using the discrete element method (DEM) for cohesive particles and the extent of discharge segregation is characterized over time. The strength of the cohesive bond is characterized by the Bond number determined with respect to the smaller particle species. As the Bond number of the system increases, the extent of discharge segregation in the system decreases. A critical value of Bo = 1 is identified as the condition where the primary mechanism of segregation in the cohesionless hopper system, i.e. gravity-induced percolation, is essentially eliminated due to the liquid bridges between particles.;Finally, experiments are performed in a hopper of identical dimensions as in the simulation to verify the model. Three specific characteristic of the flow: discharge rate, angle of repose of the material and size of clumps formed during the discharge are investigated experimentally and compared to the simulations. The simulation results agree well with the experimental results. In general, the discharge rate decreases, angle of repose increases and size of clumps increases as cohesion increases. (Full text of this dissertation may be available via the University of Florida Libraries web site. Please check http://www.uflib.ufl.edu/etd.html)
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机译：本工作使用离散元方法研究了一个准3D矩形漏斗的漏斗现象。在许多涉及粒状物料处理的工业过程中，准确预测料斗的出料速度非常重要。对于无粘性的粒状介质，研究了颗粒性质（颗粒大小和尺寸分布）和料斗几何形状（料斗宽度，出口宽度，角度和填充高度）的影响，并将其与以前发表的实验相关性进行了比较。结果表明，DEM模拟完全能够再现实验中众所周知的放电速率趋势。例如，显示出粒度和料斗宽度对排出速率具有最小的影响。此外，对于矩形漏斗，如修正的Beverloo相关性所示，出水速率随出口宽度增加到3/2功率而变化。 DEM仿真还用于探索尚未或不容易通过实验探索的更广泛的参数。例如，研究了料斗摩擦力，颗粒摩擦力和恢复系数的影响，并显示了颗粒摩擦力对料斗的排放行为有重要影响。;本工作还研究了影响湿法排放速率的参数。内聚系统。粒子之间的内聚力由一个悬臂的液体桥力模型描述，内聚键的强度由一个键数表征。通过将Beverloo常数修改为键数的函数，将Beverloo相关性应用于内聚系统。从这种修改的相关性获得的预测相当合理地拟合了模拟数据。另外，料斗角在粘性系统中的影响显示出与无粘性系统相似的趋势，在这种情况下，排放速率对料斗角的变化不敏感，但在临界角以下（相对于垂直方向）排放速率增加迅速。流动的临界角随内聚力的增加而减小。由于颗粒性质（例如大小，形状和密度）的差异，颗粒状材料容易分离。分离在涉及粒状材料的工业过程中很常见，甚至在材料均匀混合后也可能发生。这项工作的特定目标之一包括通过模拟研究由于液体桥接对颗粒分离产生的颗粒内聚的影响。具体来说，使用离散元素方法（DEM）对从3D料斗流出的双分散颗粒材料进行模拟，以分析粘性颗粒，并表征随时间变化的放电偏析程度。内聚键的强度由相对于较小颗粒种类确定的键数表征。随着系统键数的增加，系统中放电隔离的程度降低。 Bo = 1的临界值被确定为以下条件：由于颗粒之间的液桥，基本消除了无粘性料斗系统中的主要分离机理，即重力诱导的渗滤。最后，在料斗中进行了实验。具有与仿真中相同的尺寸以验证模型。实验研究了流动的三个具体特征：排放速率，材料的休止角和在排放过程中形成的团块的大小，并与模拟进行了比较。仿真结果与实验结果吻合良好。通常，随着内聚力的增加，排出速率降低，休止角增加并且团块的尺寸增加。 （可通过佛罗里达大学图书馆网站获得本文的全文。请检查http://www.uflib.ufl.edu/etd.html）
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