Flow velocity measurement and visualization using particle image velocimetry and fluorescent dye were carried out for a viscoelastic fluid flow in a serpentine microchannel for the purpose to quantitatively evaluate the unsteady flow characteristics that is observed even under very low Reynolds number regime due to the combined effect of the viscoelastic fluid properties and the channel shape. Sucrose water solution (Newtonian fluid) and the polyacrylamide-sucrose water solution (viscoelastic fluid) were used as working fluids. The mixing performance markedly increased when the Reynolds number exceeded a certain value in the polyacrylamide solution case. The single-point, cross-sectional and two-dimensional velocity distributions showed that low frequency fluctuation was produced in the polyacrylamide solution case. Particularly large fluctuation in the channel spanwise direction was observed in the upstream area of the serpentine channel. On the other hand, the amplitude of the fluctuation decreased in the downstream region. The fluctuation in the upstream region is believed to be generated by the flow instability at the curved part of the channel, while the fluctuations in the downstream area were attributed to the local instability and the vortices provided from the upstream region.
[1]
Y. Joo,et al.
Observations of purely elastic instabilities in the Taylor–Dean flow of a Boger fluid
,
1994,
Journal of Fluid Mechanics.
[2]
Victor Steinberg,et al.
Efficient mixing at low Reynolds numbers using polymer additives
,
2001,
Nature.
[3]
Ronald G. Larson,et al.
A purely elastic instability in Taylor–Couette flow
,
1990,
Journal of Fluid Mechanics.
[4]
Victor Steinberg,et al.
Chaotic flow and efficient mixing in a microchannel with a polymer solution.
,
2003,
Physical review. E, Statistical, nonlinear, and soft matter physics.