Bifurcations in flows of complex fluids around microfluidic cylinders

Haward, Simon J.; Hopkins, Cameron C.; Varchanis, Stylianos; Shen, Amy Q.

doi:10.1039/d1lc00128k

Cited by 15 publications

(26 citation statements)

References 133 publications

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“…3D numerical simulations of viscoelastic flow past a cylinder, and a systematic experimental study that varies the channel blockage and aspect ratios, and the rheology of the test fluid will be instructive. Our results contribute to the rapidly growing understanding viscoelastic flow instabilities in microfluidic geometries, 15,24,57 and should be considered in the design of microfluidic devices and lab-on-a-chip systems that utilize viscoelastic fluids.…”

Section: Discussionmentioning

confidence: 73%

“…3(b) and (c). However, these effects are extremely weak compared with the downstream asymmetries observed for viscoelastic flow past low- B R cylinders, 20,51–58 and the flow regains symmetry beyond the distance of approximately 10 R . In the present case, by far the most significant phenomena are observed upstream of the cylinder, so we will focus on the instability that forms upstream for the remainder of this work.…”

Section: Resultsmentioning

confidence: 91%

“…Detailed experiments and numerical simulations suggest that this steady flow asymmetry arises due to a combination of extension in the wake and shear-thinning in the gaps between cylinder and walls. 20,[52][53][54][55][56][57][58] For viscoelastic flow past high-blockage-ratio microcylinders (B R Z 0.5) in low-aspect-ratio channels (a r 0.6), experiments show dynamics that are significantly different from those observed in flow past smaller blockage ratio cylinders in higher aspect ratio channels. For both constant viscosity, highly elastic polymer solutions, 59 and shear-thinning, viscoelastic wormlike micellar solutions, 60 the elastic instability results in the formation of a stagnant vortex region attached to the upstream pole of the cylinder.…”

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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Upstream wall vortices in viscoelastic flow past a cylinder

2022

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Section: Discussionmentioning

confidence: 73%

Section: Resultsmentioning

confidence: 91%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Upstream wall vortices in viscoelastic flow past a cylinder

2022

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“…A similar envelope was observed around the two closely placed cylinders, as well as a recirculation zone between the cylinders that forms at relatively small Wi, Wi = 1.88, which can be explained by the high value of β. Increasing further Wi, a transition to asymmetric flow is observed, which can be attributed to shear thinning in the FENE-P model (Haward et al 2021b).…”

Section: Cylinders Aligned With the Flowmentioning

confidence: 95%

Birefringent strands drive the flow of viscoelastic fluids past obstacles

et al. 2022

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The flow of polymer solutions past solid obstacles or through porous media gives rise to rich physical phenomena over a wide range of spatial and temporal scales. Viscoelasticity, in particular, can induce a strong nonlinear response with an increase of flow resistance even for a solution whose viscosity decreases in simple shear flow. Various hypotheses have been proposed to explain this phenomenon but a clear picture of the pore-scale mechanisms involved and their impact upon larger scales is still lacking. Here, we show that localized zones of large polymeric stress, known as birefringent strands, drive the flow of an Oldroyd-B fluid through two-dimensional arrays of cylinders. Combining a recently developed numerical scheme with high performance computing, we find that these strands generate a complete reorganization of the flow with an increase of stagnation zones, a reinforcement of preferential paths and a splitting of flow channels. Furthermore, we show that this reorganization is the source of an increase in the viscous dissipation of the solvent and also that the stretching of polymer molecules in the strands is associated with entropy production. Both these phenomena yield a global increase in dissipation that can be directly linked to the increase of flow resistance. Our results demonstrate that the birefringent strands – not the elongational viscosity – drive the flow of viscoelastic fluids through porous media and that the increase of flow resistance can occur even at steady state, before the transition to elastic turbulence.

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Perspective on the description of viscoelastic flows via continuum elastic dumbbell models

Boyko,

Stone

2024

J Eng Math

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Non-Newtonian fluid mechanics and computational rheology widely exploit elastic dumbbell models such as Oldroyd-B and FENE-P for a continuum description of viscoelastic fluid flows. However, these constitutive equations fail to accurately capture some characteristics of realistic polymers, such as the steady extension in simple shear and extensional flows, thus questioning the ability of continuum-level modeling to predict the hydrodynamic behavior of viscoelastic fluids in more complex flows. Here, we present seven elastic dumbbell models, which include different microstructurally inspired terms, i.e., (i) the finite polymer extensibility, (ii) the conformation-dependent friction coefficient, and (iii) the conformation-dependent non-affine deformation. We provide the expressions for the steady dumbbell extension in shear and extensional flows and the corresponding viscosities for various elastic dumbbell models incorporating different microscopic features. We show the necessity of including these microscopic features in a constitutive equation to reproduce the experimentally observed polymer extension in shear and extensional flows, highlighting their potential significance in accurately modeling viscoelastic channel flow with mixed kinematics.

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Bifurcations in flows of complex fluids around microfluidic cylinders

Abstract: We review recent work examining flow asymmetries observed for viscoelastic shear-thinning fluids around obstacles in microchannels, and provide a mechanism for the instability.

Cited by 15 publications

References 133 publications

Upstream wall vortices in viscoelastic flow past a cylinder

Upstream wall vortices in viscoelastic flow past a cylinder

Birefringent strands drive the flow of viscoelastic fluids past obstacles

Perspective on the description of viscoelastic flows via continuum elastic dumbbell models

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