Fine particle percolation in a sheared granular bed

TL;DR

This study investigates how fine particles percolate through a sheared granular bed, revealing how percolation velocity varies with shear rate and particle size ratio, especially around the free-sifting threshold.

Contribution

It provides new insights into the percolation dynamics of fine particles in sheared granular beds, especially across different size ratios and shear conditions.

Findings

Percolation velocity increases then decreases with shear rate for R<R_t.

Percolation velocity remains constant then decreases for R>R_t.

Fine-particle excitation influences percolation behavior at high shear rates.

Abstract

We study the percolation velocity, $v_p,$ of a fine spherical particle in a sheared large-particle bed under gravity using discrete element method simulations for large-to-fine particle diameter ratios, $R=d/d_f,$ below and above the free-sifting threshold, $R_t\approx6.5.$ For $R<R_t,$ $v_p$ initially increases with increasing shear rate, $\dot\gamma,$ as shear-driven bed rearrangement reduces fine-particle trapping but then decreases toward zero due to fine-particle excitation for $\dot\gamma\sqrt{d/g}\gtrsim 0.1$. For $R>R_t$, $v_p$ is constant at low $\dot\gamma$ but decreases toward zero at higher shear rates due to fine-particle excitation.