Extensional Flows of Polymer Solutions in Microfluidic Converging/Diverging Geometries

Gareth H. Mckinley(1), Lucy Rodd (1,2), Monica Oliveria, Justin Cooper-White(3)
1 Hatsopoulos Microfluidics Laboratory, Dept. Mechanical Engineering, MIT, Cambridge MA 02139, USA
2 Dept. of Chemical and Biomolecular Engineering, The University of Melbourne, VIC 3010, Australia
3 Division of Chemical Engineering, The University of Queensland, Brisbane, QLD 4072, Australia


The effects of fluid elasticity in the flow of non-Newtonian fluids in microfluidic converging/diverging
geometries are investigated. We explore the structure and dynamics of inertio-elastic flow instabilities and elastic
corner vortices which develop upstream of the contraction plane, and explore their dependence on the relative
magnitudes of inertia and elastic stress generated by the high deformation rates in the contraction geometry. We
find that the shape, size and evolution of these flow structures varies with the elasticity number, which is
independent of the flow kinematics and is only dependent on fluid properties (viscosity, density and polymer
relaxation times) and the characteristic size of the channel.