Paper Number
NF21
Session
Non-Newtonian Fluid Mechanics & Flow Instabilities
Title
Law of resistance for viscoelastic fluids in channel flows at low Re
Presentation Date and Time
October 17, 2018 (Wednesday) 2:20
Track / Room
Track 7 / Plaza II
Authors
- Arratia, Paulo E. (University of Pennsylvania, Mechanical Engineering & Applied Mechanics)
- Qin, Boyang (University of Pennsylvania)
Author and Affiliation Lines
Paulo E. Arratia and Boyang Qin
Mechanical Engineering & Applied Mechanics, University of Pennsylvania, Philadelphia, PA
Speaker / Presenter
Arratia, Paulo E.
Text of Abstract
In this talk, we investigate the flow of a polymeric fluid in a straight micro-channel at low Re using pressure drop measurement and particle tracking methods. Pressure measurements show that the flow resistance increases as the flow transitions from stable/laminar to a "turbulent-like" state. This behavior is analogous to Newtonian fluids where the friction factor increases as the flow transitions from laminar to turbulent except that here the governing parameter is the Weissenberg number (Wi). The increased in flow resistance suggests the presence of flow structures. We find that tracer particles in the parallel shear region follows wavy trajectories with strong spanwise modulation not found in the stable unperturbed flow. Statistics of the secondary velocity component clearly suggest the presence of flow structures taking place far downstream in the parallel shear region. We believe that the increase in flow resistance is connected to the appearances of these wavy particle motions. As a result, the flow resistance, as measured by pressure head required to sustain the flow, increases markedly relative to the laminar flow.