A Simple Model for the Rheology of Concentrated Aggregating Suspensions

Abstract

A simple model for aggregation and fragmentation in concentrated suspensions (up to solids volume fractions of 20 %) is developed, based on a previous detailed sectional model describing the behavior of aggregate size distributions [1]. The entrapment of matrix liquid within the fractal-like aggregates renders the viscosity dependent on the degree of aggregation. A new fragmentation kernel is proposed accounting for particle-particle interaction forces and aggregate structure. The transient behavior of aggregate size and viscosity is studied and special focus is put on the calculation of steady state flow curves. The model predictions are validated by comparison to the detailed sectional model and to experimental results. The flow curves can be approximated by power-laws and their simulation is much faster than with the sectional model, see Fig. [1] G. Barthelmes, S. E. Pratsinis, H. Buggisch, Particle Size Distributions and Viscosity of Suspensions Undergoing Shear-Induced Coagulation and Fragmentation, Chem. Eng. Sci. 2003, in press.Figure. Steady state flow curves for varied solids volume fraction: comparison between results by the sectional model ([1], points) and the simplified model (lines).