An experimental study of the merging flow of polymer solutions in a T-shaped microchannel

Abstract

The merging flow through a T-junction is relevant to sample mixing and particle manipulation in microfluidic devices. It has been extensively studied for Newtonian fluids, particularly in the high inertial...

Elasto-inertial instabilities in the merging flow of viscoelastic fluids

“…This unsteady regime at Re Z 34.6 signifies the combined effect of fluid elasticity and inertia. Such a phenomenon is different from the observation in 1000 ppm/2 MDa PEO solution (El = 0.37) in our recent study, 55 where the state of unsteady flow starts at a much smaller Re = 4.18, way before the fluid inertia plays a significant role. This variation should be attributed to the much weaker elasticity of the fluids tested here (e.g., El = 0.039 for the PEO solution with the highest concentration of 500 ppm).…”

“…It is noted that the elasto-inertial instability in the 100 ppm/ 8 MDa PEO solution is again different from our recent observation in 1000 ppm/2 MDa solution, wherein, as noted earlier, the unsteady flow starts far before the fluid inertia takes effects. 55 As the PEO solution in our recent study actually has a smaller El = 0.37 than the 8 MDa solution (El = 0.96), we hypothesize that the polymer entanglement in terms of c/c* (see Table 1) may play the primary role here and will discuss this aspect later in the paper. Another interesting phenomenon to note is that the juxtaposition and the subsequent unsteady states can be accessed by increasing either the flow rate (i.e., fluid inertia in terms of Re as well as fluid elasticity in terms of Wi) or the polymer content including both concentration and M w (i.e., fluid elasticity in terms of El via the relaxation time).…”

“…In a recent study our group investigated the effects of fluid rheological properties on the merging flow of five types of polymer solutions including polyvinylpyrrolidone (PVP), xanthan gum (XG), hyaluronic acid (HA), PEO and PAA. 55 We observed in these solutions a direct switch from an undisturbed flow to either a steady vortical or an unsteady three-dimensional flow near the stagnation point of the T-junction with the increase of Reynolds number, depending on the strength of fluid elasticity and/ or shear thinning. The transition state in between these two types of merging flow patterns is, however, still unknown.…”

“…The T-shaped microchannel used in our recent study 55 was reused here providing the basis for a domain independent comparison of the results from the two projects. It was fabricated with polydimethylsiloxane (PDMS) using the standard soft lithography technique.…”

Microfluidics: a concise review of the history, principles, design, applications, and future outlook

“…The primary objective of their research was to systematically examine and comprehend the effects of fluid shear thinning and elasticity on the flow characteristics. 172…”