Simulating structured fluids with tensorial viscoelasticity

TL;DR

This paper introduces a novel simulation platform for modeling tensorial viscoelasticity in structured fluids, capturing microscopic details often neglected, and demonstrates how these features influence the behavior of immersed elastic bodies.

Contribution

The authors develop a tensorial viscoelastic simulation method based on lattice Boltzmann that incorporates microscopic orientation and stress diffusion, enhancing realism over existing models.

Findings

Restoring force depends non-monotonically on stress diffusion rate.

Force varies with the microscopic orientation relative to pulling direction.

The method captures complex dependencies of viscoelastic response on key parameters.

Abstract

We consider an immersed elastic body that is actively driven through a structured fluid by a motor or an external force. The behavior of such a system generally cannot be solved analytically, necessitating the use of numerical methods. However, current numerical methods omit important details of the microscopic structure and dynamics of the fluid, which can modulate the magnitudes and directions of viscoelastic restoring forces. To address this issue, we develop a simulation platform for modeling viscoelastic media with tensorial elasticity. We build on the lattice Boltzmann algorithm and incorporate viscoelastic forces, elastic immersed objects, a microscopic orientation field, and coupling between viscoelasticity and the orientation field. We demonstrate our method by characterizing how the viscoelastic restoring force on a driven immersed object depends on various key parameters as well as the tensorial character of the elastic response. We find that the restoring force depends non-monotonically on the rate of diffusion of the stress and the size of the object. We further show how the restoring force depends on the relative orientation of the microscopic structure and the pulling direction. These results imply that accounting for previously neglected physical features, such as stress diffusion and the microscopic orientation field, can improve the realism of viscoelastic simulations. We discuss possible applications and extensions to the method.