Discrete element analysis of normal elastic impact of wet particles
Discrete element analysis of normal elastic impact of wet particles
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DOI：
10.1016/j.powtec.2019.12.021
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发表时间：
2020-02
影响因子：
5.2
通讯作者：
Ling Zhang;Chuan-Yu Wu
中科院分区：
文献类型：
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作者：
Ling Zhang;Chuan-Yu Wu
颗粒材料中液体的存在会对其在加工和处理过程中的散装行为产生重大影响。众所周知，颗粒材料的整体行为是由颗粒之间的相互作用所主导的。因此，透彻地了解存在液体时的颗粒-颗粒相互作用对于解开湿颗粒材料的复杂力学和物理至关重要。本文发展了一种湿颗粒体系的离散元方法，建立了不同尺寸颗粒间摆动液桥相互作用的接触模型。为了评价DEM的精度和稳健性，系统地分析了湿颗粒与墙体的法向弹性碰撞。结果表明，DEM模拟能够准确地再现文献中报道的实验观测结果。此外，DEM分析也与弹流模型吻合较好。进一步证明了湿颗粒的回弹行为是由斯托克斯数决定的。有一个临界斯托克斯数，低于这个临界值，粒子将粘在壁面上。对于Stokes数大于临界Stokes数的碰撞，弹性粒子的恢复系数随着Stokes数的增大而增大。实验还发现，接触角和表面张力对湿颗粒的正常冲击作用不大，而液体的粘度对回弹行为起主导作用。
The presence of liquids in particulate materials can have a significant effect on their bulk behaviour during processing and handling. It is well recognised that the bulk behaviour of particulate materials is dominated by the interactions between particles. Therefore, a thorough understanding of particle-particle interaction with the presence of liquids is critical in unravelling complex mechanics and physics of wet particulate materials. In the current study, a discrete element method for wet particulate systems was developed, in which a contact model for interactions with pendular liquid bridges between particles of different sizes was implemented. In order to evaluate the accuracy and robustness of the developed DEM, normal elastic impacts of wet particles with a wall were systematically analysed. It was shown that the DEM simulations can accurately reproduce the experimental observations reported in the literature. In addition, the DEM analysis was also in good agreement with the elastohydrodynamic model. It was further demonstrated that the rebound behaviour of wet particles is dominated by the Stokes number. There was a critical Stokes number, below which the particle will stick with the wall. For impacts with a Stokes number higher than the critical Stokes number, the coefficient of restitution increases as the stokes number increases for elastic particles. It was also found that the contact angle and surface tension played an insignificant role in the normal impact of wet particles, while the viscosity of the liquid has a dominant effect on the rebound behaviour.