Flow Structures and Sorting Effects of Vibration-Driven Immersed Dense Granular Systems*

Understanding the dynamic characteristics of vibration-driven immersed dense granular systems (VIGS) is crucial for comprehending the mechanisms in applications such as ore sorting and debris flow assessment. This work, through the combination of CFD-DEM simulations and laboratory experiments, studies the dynamic characteristics of VIGS. Using a newly developed homogenization method, a macroscopic convective structure with thermodynamic similarity is found in a system of monodisperse spherical particles with the same density, verifying the critical role of granular flow structure in VIGS. To further understand the influence of the flow structure, the quasi-two-dimensional monodisperse VIGS with different density ratio conditions was experimentally studied, and the sorting effect was analyzed. It was found that the sorting effect is closely related to the state of the flow structure. The vibration intensity, the density ratio of particles to the surrounding fluid, and the fluid viscosity jointly affect the state of the flow structure, thereby influencing the sorting effect. The granular gas state of particles has a good sorting effect but requires high vibration intensity, while the Leidenfrost state with a liquefied surface is an optimal state where vibration energy input and sorting efficiency are balanced. This study might provide data and theoretical support for the sorting needs of immersed dense particles.