Berlin 2008 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 22: POSTERS Micro- and Nanofluidics
CPP 22.17: Poster
Mittwoch, 27. Februar 2008, 16:00–18:30, Poster A
On particle based velocimetry: Brownian particle near walls — •Laura Almenar1,2 and Markus Rauscher1,2 — 1Max-Planck-Institut für Metallforschung, Stuttgart, Germany — 2ITAP, Universität Stuttgart, Stuttgart, Germany
Motivated by particle based velocimetry techniques, in particular by double focus correlation spectroscopy experiments, we study the dynamics of Brownian particles in shear flow in the vicinity of planar walls. The experiments are designed to measure hydrodynamic slip in polar liquids. However, wall effects such as the fact that the particles cannot penetrate into the wall, the electrostatic double layer force, and the reduced particle mobility in the vicinity of the wall have to be taken into account in the data analysis in order to avoid spurious slip. We model the dynamics of the Brownian particles by a drift-diffusion equation taking into account the impermeability of the wall, the electrostatic double layer force, and the reduced mobility of the particles in the vicinity of the wall. The latter turns out to be irrelevant for the experimental system.
We use analytical as well as numerical tools to simulate the experiments and to quantify the spurious slip that one would measure if the data was analyzed in a naive way. Here, we find qualitative agreement with the experiment. It turns out that for a more careful analysis of experimental data one needs more detailed information on the electrostatic particle-wall interaction.