On the use of viscous micropumps for transporting viscoelastic fluids in channel flows: A numerical study

A rotating cylinder asymmetrically placed across a duct, with its axis perpendicular to the axis of the channel, has long established itself as a simple mechanism for the transport of Newtonian fluids in microfluidic channels. In the present study, the possibility of transporting viscoelastic fluids by this simple mechanism is numerically investigated using finite-volume method (FVM). For ease of analysis, we have relied on two-dimensional flow between two parallel plates for this purpose. To screen out the complicating effects of shear-dependent viscosity from the analysis, the viscoelastic fluid of interest is assumed to obey the Oldroyd-B model. Using finite-volume-method (RheoFoam solver) we have obtained converged creeping-flow results over a wide range of working parameters for Deborah numbers up to unity. Based on our obtained numerical results, it is concluded that a fluid's elasticity can negatively affect the performance of viscous micro-pumps. The drop in efficiency is predicted to increase the larger the Deborah number. At De = 1, the drop in efficiency is predicted to be around 30%, as compared with Newtonian fluids of the same viscosity. Since the drop in efficiency is not too excessive, viscous micropumps can be regarded as a viable option for the transport of moderately-elastic liquids, particularly in those microfluidic applications where efficiency is of secondary importance.

Automated summary

Numerical investigation on transporting viscoelastic fluids using a simple mechanism of a rotating cylinder asymmetrically placed across a duct showed that fluid's elasticity negatively affects the performance of viscous micro-pumps. The drop in efficiency is predicted to increase with higher Deborah numbers, reaching around 30% at De = 1 compared to Newtonian fluids of the same viscosity.