Agglomerate size and infiltration behavior affecting dispersibility of fine particle clusters

The dispersion of spherical carbon black agglomerates suspended in polydimethyl siloxane (PDMS) liquid and subjected to simple shear flows has been studied in a cone-and-plate shearing device. Sets of dispersion experiments were carried out for agglomerates of various size and packing density. For agglomerates of equal density, and under conditions of equivalent cone rotation rates, the dispersion rates of small agglomerates were smaller than those observed for larger agglomerates. In order to interpret this result, three-dimensional simulations of the flow fields within the cone-and-plate device and the resulting stress fields acting on spherical agglomerates were performed. Since the agglomerates occupy a significant fraction of the flow domain, the magnitude and distribution of shear stress acting on the agglomerate depends on its size relative to the size of the gap between the cone and plate. Additional experiments, in which the peak stress acting on agglomerates of various sizes was matched, showed the dispersion kinetics still differed according to the agglomerate size. Explanations for this behavior are proposed.; Lattice-Boltzmann methods (LBM) for one-phase and two-phase flows proposed by Rothmann and Keller were examined to simulate the infiltration behavior of fluids into porous media having rectangular and spherical configurations. The sensitivity of the infiltration behavior to the physical characteristics of the system (such as porosity, permeability, degree of saturation and dimensions of the porous solid, as well as the dynamic viscosity and surface tension of the fluid) was investigated. Results of the LBM approach show good agreement with those from continuum models describing infiltration behavior. In addition, the one-phase LBM was applied to investigate the influence of pore network structure on the infiltration behavior.