Falling Jets of Particles in Viscous Fluids
  This fluid dynamics video presents experiments and simulations of gravity-driven particulate jets in viscous fluids at low Reynolds number. An initially straight jet is shown to develop varicose modulations of its diameter as it sediments under the action of gravity. While this instability is qualitatively reminiscent of the classical Rayleigh-Plateau instability for immiscible fluids, its mechanism has yet to be understood as neither inertia nor surface tension play a role in the case of a dilute suspension at Re=0. 
Florent Pignatel, Maxime Nicolas, Elisabeth Guazzelli, David   Saintillan