The sedimentation of flexible filaments: Trajectories, particle clouds and a buckling instability

TL;DR

This study investigates the complex sedimentation behaviors of flexible filaments in viscous fluids, revealing their shapes, trajectories, and instabilities through analytical and numerical methods based on slender-body theory.

Contribution

It introduces a comprehensive analysis of filament sedimentation dynamics, including shape evolution, cloud formation, and buckling instability, using a novel dimensionless elasto-gravitation number.

Findings

Filaments exhibit diverse trajectories and shapes during sedimentation.

Particle clouds form as a result of filament dynamics.

Buckling instability occurs under certain conditions.

Abstract

In this fluid dynamics video we explore an array of different possible dynamics for a flexible filament sedimenting in a viscous fluid. The time-dependent shapes and trajectories of the filament are determined analytically and numerically by balancing viscous, elastic and gravitational forces in a slender-body theory for zero-Reynolds number flows. The dynamics are characterized by a single dimensionless elasto-gravitation number. The video shows the process of filament relaxation and reorientation, the formation of particle clouds, and finally a buckling instability.