Reducing segregation in vibrated binary-sized granular mixtures by excessive small particle introduction

TL;DR

This study uses numerical simulations to show that introducing an excess of small particles in vibrated binary granular mixtures can suppress segregation and induce ordered phases among large particles.

Contribution

It demonstrates that increasing small particle fraction creates effective repulsion among large particles, reducing segregation and promoting hexagonal ordering in vibrated granular mixtures.

Findings

Small particles suppress large particle segregation.

Effective repulsion leads to hexagonal ordering.

Results are consistent across different parameters.

Abstract

We numerically examine binary-sized granular mixtures confined between two parallel walls subjected to vertical vibration using the discrete element method. For a size ratio of $3$ between large and small particles, we study the structure of large particles in moderately dense regimes where the combined two-dimensional packing fractions of both particle sizes exceed $1$. When the fraction of small particles is small, segregation of the large particles occurs. In contrast, as the fraction of small particles increases, an effective repulsion between the large particles emerges over distances greater than the large particle diameter, suppressing their segregation. The emergence of reduction in segregation is confirmed for another size ratio, vibrational acceleration, system size, and for a case of bidisperse size distribution. Additionally, at the size ratio of $3$, the effective repulsion induces a hexagonal phase of the large particles at packing fractions lower than in mono-component systems. This work will provide a fresh insight into granular physics, prompting further experimental and theoretical study.