Abstract

HERRMANN, H. J.; HARTING, J.; HECHT, M.  and  BEN-NAIM, E.. Simulation of dense colloids. Braz. J. Phys. [online]. 2008, vol.38, n.1, pp. 37-42. ISSN 0103-9733.  doi: 10.1590/S0103-97332008000100007.

We present in this proceeding recent large scale simulations of dense colloids. On one hand we simulate model clay consisting of nanometric aluminum oxyde spheres in water using realistic effective electrostatic interactions and Van der Waals attractions, known as DLVO potentials and a combination of molecular dynamics (MD) and stochastic rotation dynamics (SRD). We find pronounced cluster formation and retrieve the shear softening of the viscosity in quantitative agreement with experiments. On the other hand we study the velocity probability distribution functions (PDF) of sheared hard-sphere colloids using a combination of MD with lattice Boltzmann and find strong deviations from a Maxwell-Boltzmann distribution. We find a Gaussian core and an exponential tail over more than six orders of magnitude of probability. The simulation data follow very well a simple theory. We show that the PDFs scale with shear rate $\dot\gamma$ as well as particle volume concentration f, and kinematic viscosity n.

Keywords : Computer simulations; Molecular Dynamics; SRD; Lattice Boltzmann; Colloids; Shear cell; Rheology.