Enhancement of drag and mixing in a dilute solution of rodlike polymers at low Reynolds numbers

TL;DR

This study uses numerical simulations to show that dilute solutions of rigid rodlike polymers at low Reynolds numbers can destabilize laminar flow, leading to turbulence-like behavior that enhances mixing and increases flow resistance.

Contribution

It demonstrates how polymer rotational dynamics induce flow destabilization and turbulence-like states, improving mixing efficiency in low Reynolds number flows.

Findings

Flow destabilization due to polymer rotation

Emergence of turbulence-like chaotic flow

Enhanced mixing and increased flow resistance

Abstract

We study the dynamics of a dilute solution of rigid rodlike polymers in a viscous fluid at low Reynolds number by means of numerical simulations of a simple rheological model. We show that the rotational dynamics of polymers destabilizes the laminar flow and causes the emergence of a turbulent-like chaotic flow with a wide range of active scales. This regime displays an increased flow resistance, corresponding to a reduced mean flow at fixed external forcing, as well as an increased mixing efficiency. The latter effect is quantified by measuring the decay of the variance of a scalar field transported by the flow. By comparing the results of numerical simulations of the model in two- and three-dimensions, we show that the phenomena observed are qualitatively independent on the dimensionality of the space.