Abstract This paper presents a numerical modeling on the packing densification of uniform spheres under air impact using a combined Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM). In the whole process, the packing structure evolution, corresponding dynamics and densification mechanism are comprehensively studied. Macro and micro properties such as packing density, coordination number, radial distribution function, as well as forces in the packings at different stages are characterized and compared. The results show that air impact can realize the transition of particle packing from random loose to random close state at appropriate conditions. In this duration, the depth-averaged normal force increases linearly with the height. Meanwhile, numerous normal forces are close to the horizontal at the final packing stage due to the effect of air impact, and their distributions indicate exponential decay law. While the distribution of the fluid-particle interaction forces increases with the height. Local packing structure evolution demonstrates that the dominating densification mechanism under the air impact is ‘pushing filling’.

中文翻译：

---

CFD-DEM 模拟等球体的空气冲击致密化：结构演化、动力学和机制

摘要 本文介绍了使用组合计算流体动力学 (CFD) 和离散元方法 (DEM) 在空气冲击下均匀球体的堆积致密化的数值模拟。在整个过程中，对填料结构演化、相应的动力学和致密化机制进行了综合研究。宏观和微观特性，如堆积密度、配位数、径向分布函数以及不同阶段填料中的力被表征和比较。结果表明，在适当的条件下，空气冲击可以实现颗粒堆积从随机松散状态到随机闭合状态的转变。在此期间，深度平均法向力随高度线性增加。同时，由于空气冲击的影响，许多法向力在最终包装阶段接近水平，它们的分布表明了指数衰减规律。而流体-颗粒相互作用力的分布随着高度的增加而增加。局部填充结构演化表明，空气冲击下的主要致密化机制是“推动填充”。