Particle Size Effects in Flow-Stabilized Solids

TL;DR

This study investigates how particle size influences the formation and properties of flow-stabilized solids in colloidal suspensions, revealing a transition from thermal to athermal behavior and proposing a new permeability scaling law.

Contribution

It provides experimental insights into particle size effects on flow-stabilized solids and introduces a new permeability scaling law beyond the Carman-Kozeny model.

Findings

Flow-stabilized solid properties do not scale with Péclet number.

A transition from thermal to athermal solids occurs at higher Péclet numbers.

A new permeability scaling law better predicts the permeability of these solids.

Abstract

Flow-stabilized solids are a class of fragile matter that forms when a dense suspension of colloids accumulates against a semi-permeable barrier, for flow rates above a critical value. In order to probe the effect of particle size on the formation of these solids, we perform experiments on micron-sized monodisperse spherical polystyrene spheres in a Hele-Shaw geometry. We examine the spatial extent, internal fluctuations, and fluid permeability of the solids deposited against the barrier, and find that these do not scale with the P\'eclet number. Instead, we find distinct behaviors at higher Peclet numbers, suggesting a transition from thermal- to athermal-solids which we connect to particle-scale fluctuations in the liquid-like layer at the upstream surface of the solid. We further observe that while the Carman-Kozeny model does not accurately predict the permeability of flow-stabilized solids, we do find a new scaling which predicts the permeability.