Lattice Boltzmann simulations of a viscoelastic shear-thinning fluid

TL;DR

This paper introduces a hybrid lattice Boltzmann simulation method for viscoelastic shear-thinning fluids, capturing complex transient flow behaviors influenced by structural relaxation and nonlinear stress responses.

Contribution

It develops a novel hybrid lattice Boltzmann algorithm to simulate flow of glass-forming fluids with slow structural relaxation at the Navier-Stokes level.

Findings

Transient velocity and stress dynamics depend on channel width.

Flow behavior shows nontrivial effects of viscoelasticity and shear thinning.

Simulation captures startup and cessation flow phenomena.

Abstract

We present a hybrid lattice Boltzmann algorithm for the simulation of flow glass-forming fluids, characterized by slow structural relaxation, at the level of the Navier-Stokes equation. The fluid is described in terms of a nonlinear integral constitutive equation, relating the stress tensor locally to the history of flow. As an application, we present results for an integral nonlinear Maxwell model that combines the effects of (linear) viscoelasticity and (nonlinear) shear thinning. We discuss the transient dynamics of velocities, shear stresses, and normal stress differences in planar pressure-driven channel flow, after switching on (startup) and off (cessation) of the driving pressure. This transient dynamics depends nontrivially on the channel width due to an interplay between hydrodynamic momentum diffusion and slow structural relaxation.