The dispersion of clusters of small spherical particles (20–400 m) suspended in a liquid has been studied by subjecting them to linear two-dimensional flow fields which include pure shear as one limit pure rotation as the other with simple shear as an intermediate case. If the liquid used to form the suspension is the same as the bulk medium, dispersion proceeds in a well-defined fashion depending upon: the amount of vorticity in and the strength of the undisturbed flow, the initial radius of the cluster, the radius and volume fraction of particles. It was Found that a model based upon the assumption that the rate at which the particles leave the surface of the cluster is proportional to its surface area adequately describes the dispersion process.
When a fluid othet than that used to produce the flow was used to make the suspension from which the clusters were formed, the interfacial tension between the two liquids qualitatively changes the dispersion process. The cluster behaved as a liquid drop having finite surface tension with a viscosity dependent upon the volume fraction of particles. The effect of changing the surface tension by the addition of surface active agents was also examined.