The Physics of Flowing Dense Emulsions

Emulsions, mixtures of liquid droplets dispersed in another immiscible liquid, are fascinating physical systems that exhibit rheological behavior intermediate between that of liquids and solids. Dense emulsions typically require surfactants or other stabilizing agents to prevent coalescence between contacting droplets. While the macroscopic properties of emulsions are influenced by a wide range of chemical and physical processes, this review focuses specifically on hydrodynamic effects and on the dynamics of droplet coalescence and breakup, which are central to the flow behavior of dense emulsions. We discuss three key aspects: flow-driven emulsification and the droplet size distribution; the flow and rheology of emulsions, from dilute to concentrated regimes; and the mechanisms governing the destabilization of concentrated emulsions under flow, including shear-induced coalescence and microstructural transitions.