Dilatancy and pressures in suspensions

This paper focuses on the origin and implications of particle pressure and discontinuous shear thickening in concentrated suspensions. These properties are both related to the tendency of a flowing suspension to exert normal forces on the confining boundaries, thus providing a conceptual relation of the two seemingly distinct issues through a consideration of the pressure-volume relation of a flowing suspension. An overview of basic elements of suspension mechanics related to these topics is presented, including microstructure and continuum formulations based on single-phase and two-phase perspectives. The historical development of understanding of particle pressure and its influence on particle migration and that of discontinuous shear thickening are described. The mechanistic basis for the particle pressure in terms of suspension microstructure and the role of frictional contact interactions in shear thickening are described. A few open questions related to these topics are presented in conclusion.