Soft Dynamics simulation: 2. Elastic spheres undergoing a T1 process in a viscous fluid

TL;DR

This paper uses Soft Dynamics simulation to analyze the T1 rearrangement process of elastic spheres in a viscous fluid, revealing how micro-timescales influence collective behaviors beyond traditional volume fraction effects.

Contribution

It introduces a theoretical and numerical study of elastic sphere rearrangements in viscous fluids, highlighting the role of micro-timescales in collective behaviors.

Findings

T1 process duration varies with initial separations

Micro-timescales influence collective behavior

Hydrodynamic and elastic interactions are modeled accurately

Abstract

Robust empirical constitutive laws for granular materials in air or in a viscous fluid have been expressed in terms of timescales based on the dynamics of a single particle. However, some behaviours such as viscosity bifurcation or shear localization, observed also in foams, emulsions, and block copolymer cubic phases, seem to involve other micro-timescales which may be related to the dynamics of local particle reorganizations. In the present work, we consider a T1 process as an example of a rearrangement. Using the Soft dynamics simulation method introduced in the first paper of this series, we describe theoretically and numerically the motion of four elastic spheres in a viscous fluid. Hydrodynamic interactions are described at the level of lubrication (Poiseuille squeezing and Couette shear flow) and the elastic deflection of the particle surface is modeled as Hertzian. The duration of the simulated T1 process can vary substantially as a consequence of minute changes in the initial separations, consistently with predictions. For the first time, a collective behaviour is thus found to depend on another parameter than the typical volume fraction in particles.