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 引用本文: 张华腾, 凡凤仙, 王志强. 颗粒毛细效应影响因素的离散元分析[J]. 力学学报, 2020, 52(2): 442-450.
Zhang Huateng, Fan Fengxian, Wang Zhiqiang. DEM ANALYSIS OF FACTORS INFLUENCING THE GRANULAR CAPILLARITY[J]. Chinese Journal of Theoretical and Applied Mechanics, 2020, 52(2): 442-450.
 Citation: Zhang Huateng, Fan Fengxian, Wang Zhiqiang. DEM ANALYSIS OF FACTORS INFLUENCING THE GRANULAR CAPILLARITY[J]. Chinese Journal of Theoretical and Applied Mechanics, 2020, 52(2): 442-450.

## DEM ANALYSIS OF FACTORS INFLUENCING THE GRANULAR CAPILLARITY

• 摘要: 颗粒毛细效应是指将一根细管插入填充有颗粒物质的容器中并对管施加竖直振动时颗粒在管内上升并最终达到一个稳定的高度的现象, 该现象为颗粒物料的逆重力输运提供了一种潜在的技术途径. 为探究颗粒毛细效应的影响因素, 采用离散元方法, 模拟再现了颗粒毛细效应过程,展示了不同管径下颗粒竖直方向速度演变特性, 考察了不同容器宽度和振动条件下颗粒最终毛细上升高度随管径的演变规律. 结果表明, 在容器宽度与粒径比为40、管振幅与粒径比为14.33、管振动频率为12 Hz情况下, 管径与粒径比D/d = 3.33时, 管内颗粒堵塞严重, 使得颗粒上升缓慢,并造成颗粒柱中断; D/d = 8.33时, 起初毛细上升高度增加迅速, 随后毛细上升高度的增大逐渐减缓, 管内颗粒在管径方向几乎不存在速度梯度; D/d =15时, 随着颗粒毛细上升高度的增大, 管内颗粒柱分离为速度截然不同的两层, 上层颗粒在管径方向几乎不存在速度梯度, 而下层颗粒存在明显的速度梯度.研究还发现, 在毛细效应能够发生的管径范围内, 存在一个对应于颗粒最终毛细上升高度最大值的临界管径, 当管径小于临界管径时, 颗粒最终毛细上升高度随管径的增大而增大, 当管径大于临界管径时, 颗粒最终毛细上升高度随管径的增大而趋于减小; 增大容器宽度,临界管径有所增大; 增大振幅、适当提高频率能够有效促进临界管径的增大.

Abstract: Granular capillarity refers to the phenomenon that when a narrow tube is vertically inserted into a container filled with particles and then set into vertical vibration, the particles rise up along the tube and eventually reach a certain height. This provides a potential technical method for the transportation of granular materials against gravity. To explore the factors influencing the granular capillarity, the processes of granular capillarity were numerically investigated using the discrete element method (DEM). On this basis, the evolutions of vertical velocities of particles at different tube diameters were shown, and the dependences of the final capillary height of the particles on the tube diameter at different container widths and vibrational parameters were examined. The results obtained under the conditions with the container-width-to-particle-diameter ratio of 40, vibration-amplitude-to-particle-diameter ratio of 14.33 and vibration frequency of 12 Hz show that at the tube-to-particle diameter ratio D/d = 3.33 severe jamming occurs for the particles in the tube, which makes the particles rise slowly and leads to a discontinuous granular column within the tube. At D/d = 8.33, the granular capillary height rises rapidly at the beginning, and then the increasing rate of the capillary height decreases gradually. In this case, there is almost no particle velocity gradient along the tube radius. However, at D/d=15, as the granular column height within the tube increases, the particles in the tube separated into two layers. In the upper layer, almost no particle velocity gradient along the tube radius is observed, whereas in the lower layer obvious velocity gradient can be found. It is also found that for the tube diameter range in which the granular capillarity can occur, there exists a critical tube diameter that corresponds to the maximal final capillary height. When the tube diameter is less than the critical tube diameter, the final capillary height increases with the tube diameter, whereas when the tube size is greater than the critical tube diameter, the final capillary height tends to decrease with the tube diameter. Moreover, increasing the container width leads to an increase in the critical tube diameter, while increasing the vibration amplitude of the tube and appropriately increasing the vibration frequency can effectively promote the increase of the critical tube diameter.

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