Jamming and Yielding in Dense Suspensions

Suspensions of particles dispersed in liquids are ubiquitous materials in industry and geophysics; relevant examples include cement and mud. At high particle concentration, in what is called a dense suspension, crowding induces multiscale interactions ranging from local, particle-level contact forces to macroscopic, system-spanning contact networks that dynamically evolve under applied shear. As the number of constraints on relative particle movement increases, the suspension viscosity rises, and eventually the material reaches a jammed state. In this review, we discuss frameworks developed to predict the rheological behavior of dense suspensions in the vicinity of jamming and describe the resulting flow-state diagram. Going beyond mean-field models, we discuss recent advances in understanding the contact network of spatially correlated particles. We also review recent developments for tailoring flow constraints at the particle level, both by particle geometry and by interactions induced by chemical bonds, which can be used to engineer the location and extent of different regimes in the flow-state diagram. We end with a set of issues and perspectives for future research, including possible ways to extend the current theoretical framework, apply simulations to suspensions comprising particles with more complex nonspherical or highly anisotropic shapes, and develop approaches to predict how molecular-scale details influence macroscopic flows.