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Stretching of viscoelastic drops in steady sliding

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Abstract

The sliding of non-Newtonian drops down planar surfaces results in a complex, entangled balance between interfacial forces and non-linear viscous dissipation, which has been scarcely inspected. In particular, a detailed understanding of the role played by the polymer flexibility and the resulting elasticity of the polymer solution is still lacking. To this aim, we have considered polyacrylamide (PAA) solutions of different molecular weights, suspended either in water or in glycerol/water mixtures. In contrast to drops of stiff polymers, drops of flexible polymers exhibit a remarkable elongation in steady sliding. This difference is most likely attributed to variation of viscous bending as a consequence of variation of shear thinning. Moreover, an “optimal elasticity” of the polymer seems to be required for this drop elongation to be visible. We have complemented experimental results with numerical simulations of a viscoelastic FENE-P drop. This has been a decisive step to unraveling how a change of the elastic parameters (e.g. polymer relaxation time, maximum extensibility) affects the dimensionless sliding velocity.

Graphical abstract: Stretching of viscoelastic drops in steady sliding

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Publication details

The article was received on 20 Feb 2017, accepted on 22 Mar 2017 and first published on 30 Mar 2017


Article type: Paper
DOI: 10.1039/C7SM00352H
Citation: Soft Matter, 2017, Advance Article
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    Stretching of viscoelastic drops in steady sliding

    S. Varagnolo, D. Filippi, G. Mistura, M. Pierno and M. Sbragaglia, Soft Matter, 2017, Advance Article , DOI: 10.1039/C7SM00352H

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