A Fluctuating Journey through Slowing Falling Particles

Particles falling through a viscous fluid interact with each other through long range interactions. Therefore, the mean velocity does not completely characterise their settling motion. Instead, individual particle motions fluctuate about the mean as the suspension microstructure constantly changes during the settling process. The first experimental evidence of this phenomenon was obtained in the seminal work of Bud Homsy with his PhD student John Ham in 1998 by measuring vertical velocities of marked particles. This talk will review some of the further developments in velocity fluctuations and dispersion of particles during quiescent sedimentation.