Liquid droplets sliding along solid surfaces are frequently observed phenomena in nature, e.g., raindrops on a leaf, and in everyday situations, e.g., drops of water in a drinking glass. Furthermore, sliding droplets (and consequently the suppression of those) are crucial in many applications such as the deicing of planes, coating and separation processes or lab-on-a-chip devices. To simulate the droplet dynamics with high accuracy, we utilize a thermodynamically consistent phase field model for large density ratios. The dynamics of the two-phase flow are described by the coupling between the Cahn-Hilliard (CH) and Navier-Stokes (NS) equations. Especially, the model allows the contact line to slide naturally along the solid surfaces and greatly reduces spurious currents even for low Capillary numbers. In addition, boundary conditions which allow for non-equilibrium contact angles and slip between the moving contact lines and the solid surface are applied. The resulting model forms a very tightly coupled and nonlinear system of equations. Therefore we carefully select the solution strategy to enable efficient and accurate large-scale simulations with millions of degrees of freedom. This includes the linearization and decoupling of the equations, preconditioned Krylov methods for the solution of the arising linear systems as well as anisotropic mesh adaption to guarantee high mesh resolutions. To show the capabilities of our approach we discuss numerous results of flows with or without a moving contact line. In particular, we investigate the influence of single microstructures with sharp corners on the instability onset of overflowing liquid films and the pinning mechanism of sliding droplets on sharp corners. Finally, we introduce the control of both the shape and position of droplets on solid surfaces through optimal contact angle distributions. We demonstrate our approach by pinning a sliding droplet at a specific position on an inclined plate with a desired shape using temporally and spatially varying contact angles.


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    Titel :

    Simulation and control of droplets and films on surfaces


    Weitere Titelangaben:

    Simulation und Kontrolle von Tropfen und Filmen auf Oberflächen


    Beteiligte:
    Bonart, Carl Henning (Autor:in) / Technische Universität Berlin (Gastgebende Institution)

    Erscheinungsdatum :

    2021



    Medientyp :

    Sonstige


    Format :

    Elektronische Ressource


    Sprache :

    Englisch



    Klassifikation :

    DDC:    629




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