Patterns of convection and distribution of binary particles under vibration and airflow

Vibration-driven immersed granular systems (VIGSs) are ubiquitous in nature and industry. However, particle dynamics in 3D VIGSs is hard to obtain directly from experiments. The resolved Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) is introduced to study a cylindrical VIGS subjected to vertical vibration focusing on particle dynamics. A Voronoi-weighted Gaussian interpolation (VWGI) method is used to convert the discrete particle information into a continuous field. The VWGI method enables the estimation of the continuous field for granular systems, especially for those with large-scale non-uniformity and heterogeneity particle distribution in local cells. The results show that the periodic variation of the system's kinetic energy is caused by the collision between the lower particles and the vibrating wall, and the particle kinetic energy decreases with height rising. A velocity spatial structure of convection, moving from the cylinder center to the sidewall, is observed in both immersed and dry systems away from the bottom. Vibration-driven particles can exhibit a similar flow structure to natural convection. Compared to the dry system, the convection strength and momentum transfer in the VIGS are higher, while the momentum diffusion is lower. The fluid restrains the particle energy acquisition and enhances the energy dissipation of the “heated” particles, while the formation of the fluid convection benefits the particle convection directionality. This resolved CFD-DEM study with the VWGI method provides useful results of the particle dynamics in VIGSs, which could provide guidance for some practical applications in minerals processing involving vibration-driven immersed granular systems.

Section: Introductionmentioning

confidence: 99%

Particle dynamics in vertical vibration-driven immersed granular systems: A study with resolved computational fluid dynamics-discrete element method

Wang,

Wei,

2023

Microfluidics of nanoparticles using vibration-mediated regulation of aggregates evolution

Zhu,

Lu,

Guo

et al. 2023

Controlling the flow of particulate matter, especially nanoparticles, requires a deep understanding of particle structure and motion. In this study, we present experimental observations and intrinsic mechanisms for controlling the nanoparticle flow using vibration-mediated regulation of aggregates evolution. Our findings demonstrate that vibration could exert significant forces on the particles, causing them held apart or would touch with less force and then leads to re-breakup process of the aggregates. Furthermore, the relationship between the vibration parameter, aggregate size, the microchannel size and flow behavior has also been revealed. Notably, the outflowing aggregates have extremely small Stokes numbers due to their high porosity, and their motion is dominated by gas drag. The relationship between particles flow rate and the size of the microchannel and vibration parameters has been identified. These results have significant implications for precise control and assembly of nanoparticles.

Relaxation and rheology in beam-vibrated granular system

Hong,

Li,

Zheng

et al. 2024

The yielding transition in dense granular matter under vibrated beams, despite its significance for animal and robotic locomotion on granular surfaces and underground structural engineering, remains underexplored. In this study, we systematically modulate the frequency and amplitude of beam vibrations through experiments and simulations to investigate the granular relaxation dynamics. We uncover dual yielding behaviors: gradual, ductile transitions in the time domain, where the system smoothly stabilizes, and abrupt, brittle transitions in the frequency domain, characterized by sharp shifts between metastable states and pronounced hysteresis, highlighting the dynamic consistency between the behavior of the beam and the granular materials. Through detailed analysis of the mesostructural evolution, encompassing particle motion, and mechanical stability, we unveil the root of the hysteresis as stemming from anomalous diffusion driven by memory effects, where the system's response is influenced by its stress history. These findings lead to the development of a nonmonotonic constitutive law that captures the unique frequency-dependent coupling between the beam and granular material. Our findings pave the way for advanced theoretical models in this domain, offering profound insights into the nuanced behaviors of vibrated granular systems.