Hydrodynamic Simulations of Colloidal Gels: Microstructure, Dynamics, and Rheology

The microstructure, dynamics, and rheology of colloidal suspensions with short-range depletion attraction and long-range electrostatic repulsion are studied using equilibrium predictions and a new algorithm for dynamic simulations. A focus is made on those combinations of attraction and repulsion that lead to the formation of gels. The effects of varying the strength of attraction (0???50kT), range of attraction (0.05???0.18a), strength of repulsion (0???54kT), and volume fraction (0.1???0.4) are investigated, where k is Boltzmann???s constant, T is the temperature, and a is the colloid radius. Hard-sphere thermodynamic perturbation theory is employed to predict equilibrium behavior. A new algorithm called Fast Lubrication Dynamics (FLD) is developed as part of this work and enables dynamic simulations including the effects of many-body hydrodynamic interactions, Brownian motion, and interparticle interactions at a speed more than 100 times faster than Stokesian Dynamics (SD) while retaining much of the relevant physics of SD. In addition, FLD is found to be nearly as fast as Brownian Dynamics (BD) due to the larger time steps allowed by FLD. The results of FLD simulations are compared with those of BD simulations as well as experimental results.Department of Energy, DE-FG02-97ER25308unpublishednot peer reviewe