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|Title:||Emergent patterns and stable interfaces during radial displacement of a viscoelastic fluid|
Kalpathy, Sreeram K.
|Citation:||Colloids and Surfaces -A, 2021, Vol.629, Article -127405|
|Abstract:||The displacement of a more viscous fluid by a less viscous fluid renders the fluid-fluid interface unstable and leads to intricate patterns called viscous fingers. Since the fluids experience shear during displacement, it should be possible to influence the emergence of patterns and instability dynamics through control of rheological parameters, such as elasticity or relaxation time in case of a viscoelastic fluid. In this article, we record and analyze the interfacial fingering patterns that emerge when a Newtonian fluid (glycerol-water mixtures of different viscosities) displaces a shear-thinning viscoelastic fluid (aqueous cornstarch suspensions of varying concentrations) in a radial Hele-Shaw cell geometry. While Newtonian-non-Newtonian fluid pair displacements have drawn attention of researchers in the past, the current work showcases the various regimes of emergent patterns over a wide range of viscosity ratios of the two fluids, and the effect of fluid elasticity on the rate of its displacement. As the ratio of viscosities of the inner and outer fluids is increased, radial branched patterns are replaced by more stable interfaces that display finger coalescence. Increasing the viscosity of the displacing fluid and the concentration-dependent elasticity of the outer viscoelastic fluid both lead to significant suppression of interfacial instabilities. A linear stability analysis of the interface, using viscosity ratio as the only control parameter, is employed to predict the dominant wavelength of interfacial perturbation. The perturbation wavelength computed numerically is found to match closely with the spacing between fingers measured experimentally at the onset of interfacial instability. It is suggested that control of instabilities during miscible displacement of a viscoelastic fluid (mud slurries, for example) by a Newtonian fluid has implications in material processing, such as in ensuring minimal mixing of phases while maximizing sweep efficiency during material recovery.|
|Copyright:||2021 Elsevier B.V.|
|Appears in Collections:||Research Papers (TP)|
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