Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Micro and Nano Fluidics I: Liquids at structured materials

CPP 26.2: Vortrag

Mittwoch, 27. Februar 2008, 14:30–14:45, C 264

Simulation of fluid flow in hydrophobic rough microchannels — •Jens Harting and Christian Kunert — Institute for Computational Physics, Pfaffenwaldring 27, D-70569 Stuttgart

Surface roughness becomes relevant if typical length scales of the system are comparable to the scale of the variations as it is the case in microfluidic setups. Here, an apparent boundary slip is often detected which can have its origin in the misleading assumption of perfectly smooth boundaries. We investigate the problem by means of lattice Boltzmann (LB) simulations and introduce an ``effective no-slip plane'' at an intermediate position between peaks and valleys of the surface. Our simulations show good agreement with analytical results for sinusoidal boundaries, but can be extended to arbitrary geometries and experimentally obtained surface data which cannot be treated analytically. We find that the detected apparent slip is independent of the detailed boundary shape, but only given by the distribution of surface heights. Further, we show that the slip diverges as the amplitude of the roughness increases which highlights the importance of a proper treatment of surface variations in very confined geometries. At last, we extend out work to rough hydrophobic surfaces and show that the coupling of both effects can lead to non-linear effects.