Dresden 2006 – scientific programme
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CPP: Chemische Physik und Polymerphysik
CPP 24: POSTER Microfluidics
CPP 24.2: Poster
Thursday, March 30, 2006, 17:00–19:00, P2
Free-Surface shapes of strongly deformed driven micro-droplets — •Michael Schindler1, Peter Talkner1, Peter Hänggi1, and Uwe Thiele2 — 1Institut für Physik, Universität Augsburg — 2MPI Physik Komplexer Systeme, Dresden
We propose a Finite-Element algorithm to compute free surface shapes that are significantly deformed by an applied static (gravitation) or dynamic (surface-accoustic waves) driving. In the micro-fluidic regime, where the surface tension forces become important the central difficulty resides in the approximation of the discretized curvature. We present a method how the discretization of the free surface can automatically be kept regular using a smooth transition to the behaviour of a rubber band.
By employing a variational approach we can show that the surface position must be discretized with the same order of accuracy as the velocity components. Otherwise, the free-surface boundary problem will be inconsistently formulated and give rise to approximation errors, as numerical observations confirm.
As examples we show pending pinned droplets on a flat substrate under the sole influence of gravity and capillarity and also droplets driven by surface-acoustic waves. In the limit of droplets with small equilibrium contact angles the results of our Finite-Element technique are compared to results of a lubrication approximation model.