Particle-laden flows are encountered in countless technological applications and natural processes, thus playing a pivotal role in the field of multiphase flow. What is fascinating about particle-laden flows is their marked multiscale nature, which is accompanied by a variety of small-scale phenomena that govern the macroscopic flow behavior. Because of this, modeling, measuring and simulating the dynamics of the particles and their interaction with the flow has always posed formidable challenges to the scientific community. Despite these challenges, the combined efforts of the community have led to significant progress in the understanding of the fundamental aspects, which we survey in this synoptic review. In particular, we explore the different features of particle–fluid interaction and their dependence on the particle and flow properties. Starting from the case of a single particle interacting with the flow, we discuss situations of increasing complexity like particle–particle interactions and collective particle dynamics. Situations in which particles evolve in complex flows, in particular turbulent ones, or inside complex fluids, e.g. non-Newtonian ones, are also discussed. The review ends by providing an outlook on the future directions that are expected to drive research in the coming years and the open issues that must be addressed to ensure further progress of the knowledge.
