Effects of viscoelasticity on shear-thickening in dilute suspensions in a viscoelastic fluid

TL;DR

This study uses direct numerical simulations to explore how fluid elasticity, characterized by Weissenberg number and viscosity ratio, influences shear-thickening behavior in dilute suspensions within a viscoelastic fluid, revealing complex flow-polymer interactions.

Contribution

It introduces a novel simulation approach to analyze the effects of fluid elasticity on shear-thickening, highlighting the role of viscosity ratio in modulating polymer stress and flow dynamics.

Findings

Polymer stress growth rate is suppressed at higher viscosity ratios.

Flow and conformation dynamics around particles are significantly affected by viscosity ratio.

Polymer stress modulates flow, leading to suppression of polymer stretch at large viscosity ratios.

Abstract

We investigate previously unclarified effects of fluid elasticity on shear-thickening in dilute suspensions in an Oldroyd-B viscoelastic fluid using a novel direct numerical simulation based on the smoothed profile method. Fluid elasticity is determined by the Weissenberg number Wi and by viscosity ratio $1-\beta=\eta_p/(\eta_s+\eta_p)$ which measures the coupling between the polymer stress and flow: $\eta_p$ and $\eta_s$ are the polymer and solvent viscosity, respectively.As $1-\beta$ increases, while the stresslet does not change significantly compared to that in the $\beta\to 1$ limit, the growth rate of the normalized polymer stress with Wi was suppressed.Analysis of flow and conformation dynamics around a particle for different $\beta$ reveals that at large $1-\beta$, polymer stress modulates flow, leading to suppression of polymer stretch.This effect of $\beta$ on polymer stress development indicates complex coupling between fluid elasticity and flow, and is essential to understand the rheology and hydrodynamic interactions in suspensions in viscoelastic media.