Falling Jets of Particles in Viscous Fluids

TL;DR

This study investigates the behavior of gravity-driven particle jets in viscous fluids at low Reynolds number, revealing varicose instabilities similar to Rayleigh-Plateau but driven by different mechanisms.

Contribution

It provides experimental and simulation insights into the instability mechanisms of particulate jets in viscous fluids at Re=0, a phenomenon not explained by inertia or surface tension.

Findings

Jets develop varicose modulations during sedimentation.

The instability resembles Rayleigh-Plateau but differs in mechanism.

Mechanism remains unclear due to absence of inertia and surface tension.

Abstract

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.