Flow Resistance & Structures in Viscoelastic Channel Flows at Low Re
Boyang Qin, Paul Salipante, Steven D. Hudson, Paulo E. Arratia
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 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 are found to generate sufficient hoop stresses to sustain the flow instabilities in the parallel shear flow.