Radial filtration in highly concentrated suspensions undergoing constant-force squeeze flow and its effect on the normal stress distribution

Liquid-phase migration and jamming of the suspended particles appear to be the cause of the previously reported drastic changes in the normal stress distribution in concentrated suspensions subjected to squeeze flow as the initial volume fraction is raised above a critical value. Liquid-phase migration was found to depend on the initial volume fraction of solids, the viscosity of the suspending fluid, and the size of the particles. Under some conditions, liquid-phase migration did not take place to any significant degree; however, under other conditions, the volume fraction of solids increased throughout the sample, but especially in the central region, as liquid was expelled from the test region in preference to the solids. Criteria for the occurrence of liquid-phase migration in suspensions undergoing squeeze flow are discussed in terms of dimensionless groups.