Nonuniform distribution of aggregates in a suspension flowing around a solid body

A flow of a highly concentrated latex suspension around a solid body in a thin layer between two parallel glass plates was observed by an optical microscope. A clear region, where suspended particles were rare, appeared near the rear stagnation point of the body. A model for explaining this phenomenon is proposed, in which the area of the clear region depends on an average size of aggregates of suspended particles. A possibility is suggested to use this phenomenon for measuring aggregate size in concentrated suspensions.