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Type: Text × Subject: numerical solution ×

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    Interface morphologies in liquid/liquid dewetting
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2010) Kostourou, Konstantina; Peschka, Dirk; Münch, Andreas; Wagner, Barbara; Herminghaus, Stephan; Seemann, Ralf
    The dynamics and morphology of a liquid polystyrene (PS) film on the scale of a hundred nanometer dewetting from a liquid polymethylmethacrylate (PMMA) film is investigated experimentally and theoretically. The polymers considered here are both below their entanglement lengths and have negligible elastic properties. A theoretical model based on viscous Newtonian flow for both polymers is set up from which a system of coupled lubrication equations is derived and solved numerically. A direct comparison of the numerical solution with the experimental findings for the characteristic signatures of the cross-sections of liquid/air and liquid/liquid phase boundaries of the dewetting rims as well as the dewetting rates is performed and discussed for various viscosity ratios of the PS and PMMA layers.
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    Thin-film models for viscoelastic liquid bi-layers
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2015) Jachalski, Sebastian; Münch, Andreas; Wagner, Barbara
    In this work we consider a two-layer system of viscoelastic liquids of corotational Jeffreys type dewetting from a Newtonian liquid substrates. We derive conditions that allow for the first time the asymptotically consistent reduction of the free boundary problem for the two-layer system to a system of coupled thin-film equations that incorporate the full nonlinear viscoelastic rheology. We show that these conditions are controlled by the order of magnitude of the viscosity ratio of the liquid layers and their thickness ratio. For pure Newtonian flow, these conditions lead to a thin-film model that couples a layer with a parabolic flow field to a layer described by elongational flow. For this system we establish asymptotic regimes that relate the viscosity ratio to a corresponding apparent slip. We then use numerical simulations to discuss the characteristic morphological and dynamical properties of viscoelastic films of corotational Jeffreys type dewetting from a solid as well as liquid substrate.