Scaling particle-size segregation in wide-ranging sheared granular flows

TL;DR

This study uses DEM simulations to examine how particle size segregation in sheared granular flows varies across different shear-rate regimes, revealing limitations of existing scaling laws outside moderate inertial numbers.

Contribution

It demonstrates the breakdown of existing shear-rate scaling laws in non-moderate inertial regimes and highlights the need for more comprehensive models.

Findings

Scaling laws hold only within 0.01 < I < 0.1

Continuum models mispredict segregation outside this range

Segregation dynamics vary significantly across shear regimes

Abstract

Scaling relationships have been proposed to describe shear-driven size segregation based on intruder experiments and simulations. While these models have shown agreement with experimental and numerical results under uniform shear rate, their validity across varying shear-rate conditions remains uncertain. Here, we employ Discrete Element Method (DEM) simulations to investigate particle size segregation in sheared granular flows under wide-ranging shear-rate conditions. We find that the scaling between segregation velocity and local rheological conditions holds only within a moderate inertial number range ($0.01 < I < 0.1$), and breaks down in both quasi-static and collisional regimes. Furthermore, we show that this discrepancy leads continuum models to mispredict segregation rates in bidisperse mixtures. These findings emphasize the need for more generalized scaling laws capable of capturing segregation dynamics across a broader spectrum of shear-rate conditions and regimes.