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The effect of microstructure on the flow of granular materials: Simple shear and gravity-driven flow.

机译：微观结构对粒状材料流动的影响：简单的剪切和重力驱动的流动。

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摘要

Although the transport of bulk solids materials is an integral part of many industrial processes, the effect of microstructure formation, on the flow of granular material is not fully understood. In this work a particle dynamic computer simulation is used to investigate how microstructure affects the flow properties of grains in simple shear and gravity flow in a channel. The simulation used for this study is an event driven algorithm and simulations of large systems for long times have been performed due to the fact that the dynamics of large systems are often quantitatively and qualitatively different from those of small systems.; In this work, by varying the parameters of the system, the effect of clustering has been examined for simply sheared systems of inelastic disks and spheres. It was found that the long time average stresses and granular temperature initially increased with the system size and then approached limiting values as the size of the system was further increased. It was also observed that the distribution of stresses initially broadened with system size and then approached limiting distributions as the size of the system was further increased. Combining the values of the stresses obtained from our simulations with a previous theory for the clustering length scale, it has been determined that once clusters are fully formed in a system, the stresses no longer increase. These results suggest that under certain circumstances a small system can capture the overall behavior of a much larger system.; During rapid gravity-driven flow of granular material in a channel, three distinct forms of microstructure (a plug flow, sinusoidal waves and a clumped flow) are identified. The parameters of the system, which are shown to affect structure, include average solids fraction, coefficient of restitution, particle size, the size of the periodic cell, and the distance between confining walls. Local and global steady flow properties of the system, such as velocity, mass flux, granular temperature and stresses are also examined. Finally, the types of microstructure observed by our simulations are compared to those that are predicted using a linear stability analysis of equations of motion of rapid granular flow and good agreement is found.
机译：尽管散装固体材料的运输是许多工业过程中不可或缺的一部分，但尚未完全了解微结构形成对粒状材料流动的影响。在这项工作中，使用粒子动态计算机仿真来研究微观结构如何影响通道中简单剪切和重力流中晶粒的流动特性。本研究中使用的仿真是事件驱动算法，由于大型系统的动力学通常在数量和质量上都不同于小型系统，因此已经对大型系统进行了长时间的仿真。在这项工作中，通过改变系统的参数，已经研究了非弹性圆盘和球体的简单剪切系统的聚类效果。发现长时间平均应力和颗粒温度最初随着系统尺寸的增加而增加，然后随着系统尺寸的增加而接近极限值。还观察到，应力的分布最初随着系统大小而变宽，然后随着系统大小的增加而接近极限分布。结合从我们的仿真中获得的应力值和关于簇长尺度的先前理论，可以确定一旦在系统中完全形成簇，应力将不再增加。这些结果表明，在某些情况下，小型系统可以捕获大型系统的整体行为。在通道中由重力驱动的粒状材料快速流动过程中，确定了三种不同形式的微结构（塞流，正弦波和成团流）。该系统的参数显示出会影响结构，包括平均固体分数，恢复系数，粒度，周期池的大小以及围壁之间的距离。还检查了系统的局部和全局稳态流特性，例如速度，质量通量，颗粒温度和应力。最后，将通过我们的模拟观察到的微观结构类型与使用快速颗粒流运动方程的线性稳定性分析所预测的微观结构类型进行比较，并且发现了良好的一致性。

著录项

  • 作者

    Liss, Elizabeth Dee.;

  • 作者单位

    Rutgers The State University of New Jersey - New Brunswick.;

  • 授予单位 Rutgers The State University of New Jersey - New Brunswick.;
  • 学科 Engineering Chemical.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 191 p.
  • 总页数 191
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 化工过程（物理过程及物理化学过程）;
  • 关键词

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