Flow Resistance and Structures in Viscoelastic Channel Flows at Low Re

TL;DR

This study investigates viscoelastic fluid flow in channels at low Reynolds numbers, revealing two flow regimes, flow resistance laws, and flow instabilities driven by polymer-induced hoop stresses.

Contribution

It provides new insights into flow resistance behavior and flow instabilities in low-Re viscoelastic channel flows, supported by experimental measurements and particle tracking.

Findings

Identification of two flow regimes: transitional and turbulent-like.

Establishment of flow resistance law via pressure measurements.

Observation of flow instabilities driven by hoop stresses.

Abstract

The flow of viscoelastic fluids in channels and pipes remain poorly understood, particularly at low Reynolds numbers. Here, we investigate the flow of polymeric solutions in straight channels using pressure measurements and particle tracking. The law of flow resistance is established by measuring the flow friction factor $f_{\eta}$ versus flow rate. Two regimes are found: a transitional regime marked by rapid increase in drag, and a turbulent-like regime characterized by a sudden decrease in drag and a weak dependence on flow rate. Lagrangian trajectories show finite transverse modulations not seen in Newtonian fluids. These curvature perturbations far downstream can generate sufficient hoop stresses to sustain the flow instabilities in the parallel shear flow.