arXiv subjects

Tomás Trewhela

Publications and source records attributed to Tomás Trewhela.

5 recordsLinked to original sources

arXiv2026

Shear-driven mixing of segregated granular materials

As granular materials flow and settle, interactions among particles of different sizes or properties drive mixing and segregation, producing dynamics that shape systems ranging from silos to asteroids. A hallmark of polydisperse granular flows is shear-driven size segregation, in which larger grains tend to rise above smaller ones through particle-scale rearrangements. Despite substantial progress in modeling granular flow and segregation, the complementary process of granular mixing remains less well understood. Here, we investigate the evolution of initially segregated dense granular materials driven out of equilibrium by imposed shear. We ask: what controls the extent and rate of mixing and restratification in a sheared bidisperse granular flow? Addressing this question is essential for understanding how external forcing disrupts or reinforces particle-size organization, and for optimizing processes that require controlled mixing. Using theoretical analysis and numerical simulations, we develop a framework that quantifies the degree of mixing and segregation dynamics of dense bidisperse granular flows. Our results identify the controlling roles of particle-size ratio and the Péclet number, clarify the conditions under which segregated states persist or are transiently homogenized, and provide a basis for improved prediction and control of granular mixtures in natural and industrial settings.

cond-mat.soft↗

arXiv2026

Quantum Enhancement of Particle-Size Segregation

Segregated states based on particle size emerge in granular materials from the competition between segregation and diffusive remixing. Here, we show that quantum coherence can enhance segregation beyond this classical limit. We introduce an open quantum cellular automaton for bidisperse mixtures that combines coherent transport and dissipative segregation. The automaton reproduces experimental and continuum-theory segregation dynamics, with segregation degrees collapsing onto a theoretical Péclet-dependent relationship. However, weakly decohering systems exhibit a coherence-driven transport regime that produces more strongly segregated steady states than classical predictions. Across a broad parameter range, the steady-state degree of segregation collapses onto two dimensionless numbers governing the competition between segregation, diffusion, and decoherence. These results identify quantum coherence as a mechanism for enhancing particle-size segregation and establish a framework for studying transport phenomena in open many-body systems.

cond-mat.soft↗

arXiv2026

Stress network dynamics influence on large particle segregation

A plethora of natural and industrial shear-driven granular flows exhibit particle-size segregation. Its occurrence is commonly attributed to two primary mechanisms: kinetic sieving and squeeze expulsion. While kinetic sieving is relatively well understood, squeeze expulsion lacks a clear mechanical explanation and direct experimental evidence due to difficulties in measuring stresses in granular media. Here, we investigate force networks around a large intruder in a bidimensional granular shear cell. We use transparent, birefringent disks to visualize stress chains via photoelasticity. Experiments were conducted with two different granular media to study force chains over size ratios between the intruder and surrounding particles of 1.25 to 4.0. Particle Tracking Velocimetry and G-square analysis are used to quantify particle trajectories and identify active grains. These methods enable us to measure force-chain lengths and structures around the intruder through the gap factor. Our results confirm that squeeze-expulsion strongly depends on stress transmission. Larger size ratios lead to longer force chains and greater particle participation in the global stress network. In parallel, stress fluctuations predominate in driving or restraining intruder motion by forming anisotropic force chains. These findings advance the understanding of granular segregation by clarifying the link between force-network dynamics and segregation mechanics.

cond-mat.soft↗

arXiv2025

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

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.

cond-mat.soft↗

arXiv2024

Energetics of particle-size segregation

We introduce a continuum framework for the energetics of particle-size segregation in bidisperse granular flows. Building on continuum segregation equations and a recent segregation flux model, the proposed framework offers general analytical expressions to study the physics of granular flows from a mechanical energy perspective. To demonstrate the framework's applicability, we examined the energetics in shear-driven flows. Numerical experiments with varying frictional coefficients and particle-size ratios revealed two distinct phases in the associated energetics with particle segregation and diffusive remixing, and that the potential energy to the kinetic energy ratio in the steady state follows the scaling relationship $\hat{E}^{(s)}_{gp} / \hat{E}^{(s)}_{k} \propto Pe^{-1/2}_{sr}$ for $0.4 \leq Pe_{sr} \leq 300$, the segregation-rheology Péclet number. Our findings hint that the bulk segregation-mixing state can be predicted and controlled using $Pe_{sr}$, determined from known system parameters, providing a impactful tool for engineering and geophysical applications.

cond-mat.soft↗