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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 49: Poster: Surfaces, Interfaces, Thin Films, Nanostructures

CPP 49.14: Poster

Mittwoch, 22. März 2017, 18:30–21:00, P2-OG1

Pinned and Sliding Drops -- Bifurcations and Statistics — •Sebastian Engelnkemper, Markus Wilczek, Svetlana Gurevich, and Uwe Thiele — Institut für Theoretische Physik, Westfälische Wilhelms-Universität, Corrensstr. 2, 48149 Münster

The long-wave evolution equation for a liquid film (thin-film equation) describes the dynamics of free surface structures (e.g., drops and ridges) on solid substrates. On homogeneous substrates all structures move for any applied lateral driving force (e.g., inclining the substrate). They change their shape and may at a critical driving force undergo a pearling instability where large drops emit small satellite drops [1]. On heterogeneous substrates (e.g., with a wettability pattern) drops remain pinned at more wettable spots even at small driving force. At a critical driving the drops undergo a depinning transition as analyzed for 2d drops in [2]. Here we implement the thin-film equation in the continuation-toolbox PDE2PATH [3] and analyze shape changes of 3d sliding and pinned drops on homo- and heterogeneous substrates, respectively. Main control parameters are drop volume and substrate inclination. The pearling instability of sliding drops is identified as a global bifurcation of stationary sliding drops [4]. Finally, the single-drop continuation results are related to the drop size statistics obtained in direct simulations of large drop ensembles. [1] T. Podgorski et al., Phys. Rev. Lett. 87, 036102 (2001); [2] U. Thiele, et al., NJP 8, 313 (2006); [3] H. Uecker et al., arXiv:1208.3112v2 (2012); [4] S. Engelnkemper et al., Phys. Rev. Fluids 1, 073901 (2016);