湿颗粒堆力学特性的离散元法模拟研究

Discrete element simulation of mechanical properties of wet granular pile

利用基于线性黏聚接触模型的离散元法对不同颗粒系统的堆积过程进行了数值模拟研究,分析了颗粒形状和湿颗粒间液桥力对颗粒堆积形态的影响机理,获得了球形和块状湿颗粒堆基底表面所受的法向力以及堆中颗粒间的法向力和切向力"中心凹陷"式的分布规律,讨论了颗粒形状和黏聚能量密度对基底表面作用力和颗粒间作用力的影响.研究结果表明,颗粒形状和液桥力对颗粒堆的堆积形态具有显著的影响.堆积角随着黏聚能量密度的增加而增大,并且相同条件下的块状颗粒堆积角大于球形颗粒.颗粒形状和黏聚能量密度对基底表面所受作用力和堆中颗粒间的作用力变化及最大幅值均有影响作用.当黏聚能量密度值逐渐增大时,颗粒堆的作用力最大幅值均逐渐增大,并且块状颗粒堆的作用力最大幅值大于球形颗粒堆.当黏聚能量密度值过大时,颗粒堆力学特性更加复杂,液桥力对颗粒堆积特性的影响作用大于颗粒形状的影响.

Discrete element method （DEM） simulations for pile-up processes of different particle systems were performed basedon linear cohesion contact model. Effects of particle shape and liquid bridge force between wet particles on the piling form were analyzed. The significant central dip profiles of normal force acting on the base surface, normal force and tangential force between particles were predicted. Effects of particle shape and cohesion energy density on the forces on the base surface and inter-particles were described. The results show that particle shape and the liquid bridge force have significant impacts on the piling form. With the increase of the cohesion energy density the angle of repose for each granular pile increases. But the angle of repose of cubical particles is bigger than that of spherical particles under the same condition. Particle shape and the liquid bridge force also significantly affect the change and the maximum amplitude of the forces acting on the base surface and the forces between the particles. The maximum amplitude of the forces increases with the increase of the cohesion energy density, and the value of the maximum force on cubical particles is bigger than that on spherical particles. When the value of cohesion energy density is very large, the mechanical properties of granular piles become more complicated, so that the liquid bridge force has a larger impact on the packing characteristic of particles than the impact on particle shape.