Berlin 2008 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 20: POSTERS Driven Soft Matter
CPP 20.12: Poster
Mittwoch, 27. Februar 2008, 16:00–18:30, Poster A
Constitutive equation for dense colloidal dispersions — Brader Joe M.1, Voigtmann Thomas2, Cates Michael E.2, and •Fuchs Matthias1 — 1Fachbereich Physik, Universität Konstanz, Germany — 2SUPA, School of Physics, The University of Edinburgh, UK
We present a first principles approach to the rheology of dense colloidal suspensions subject to homogeneous but otherwise arbitrary flow. Starting from the fundamental Smoluchowski equation for interacting Brownian particles neglecting hydrodynamic interactions we derive exact results for calculating time dependent averages, which lead e.g. to a generalized Green-Kubo relation for the stress tensor. Using Mori-Zwanzig type projection operator steps we develop a formally exact equation of motion for the transient density correlator which captures structural relaxation under flow. Approximations to these quantities are then developed which lead to a general constitutive equation for dense dispersions under arbitrary homogeneous flow. As the approximations used are tailored to treat high density systems our final equations allow the time dependent rheology of glassy colloidal suspensions to be investigated. We demonstate the effectiveness of our approach by presenting numerical results for shear [1] and general flows, including step-strain/compression, steady-shearing and creep.
[1] J. Brader et al., Phys. Rev. Lett. 89, 058301 (2007); M. Fuchs and M.E. Cates, Phys. Rev. Lett. 89, 248304 (2002)