Spatial cooperativity in microchannel flows of soft jammed materials: A mesoscopic approach

TL;DR

This paper presents a mesoscopic model for soft jammed materials flowing in microchannels, revealing how elastic interactions and boundary roughness influence flow behavior and spatial cooperativity.

Contribution

It introduces a mechanically-consistent mesoscopic elastoplastic model to explain non-local flow effects and boundary influences in confined amorphous solids.

Findings

Shear rate fluctuations occur in quiescent regions.

Velocity profiles deviate due to non-local effects.

Wall roughness causes large deviations linked to particle asperities.

Abstract

The flow of amorphous solids results from a combination of elastic deformation and local structural rearrangements, which induce non-local elastic deformations. These elements are incorporated into a mechanically-consistent mesoscopic model of interacting elastoplastic blocks. We investigate the specific case of channel flow with numerical simulations, paying particular attention to situations of strong confinement. We find that the simple picture of plastic events embedded in an elastic matrix successfully accounts for manifestations of spatial cooperativity. Shear rate fluctuations are observed in seemingly quiescent regions, and the velocity profiles in confined flows at high applied pressure deviate from those expected in the absence of non-local effects, in agreement with experimental data. However, we suggest a different physical origin for the large deviations observed when walls have rough surfaces, associated with "bumps" of the particles against the asperities of the walls.