Torques on curved atmospheric fibres

TL;DR

This paper develops a model for the settling and orientation of curved microplastic fibres in the atmosphere, highlighting the role of inertial torques in their alignment and transport.

Contribution

It introduces a novel model for curved fibre settling in air, emphasizing inertial torques as key to understanding their orientation during transport.

Findings

Inertial torques can align fibres at oblique angles with gravity.

The model explains recent laboratory observations of fibre orientation.

Inertial effects are significant for atmospheric particle transport.

Abstract

Small particles are transported over long distances in the atmosphere, with significant environmental impact. The transport of symmetric particles is well understood, but atmospheric particles, such as curved microplastic fibres or ash particles, are generally asymmetric. This makes the description of their transport properties uncertain. Here, we derive a model for how planar curved fibres settle in quiescent air. The model explains that fluid-inertia torques may align such fibres at oblique angles with gravity as seen in recent laboratory experiments, and shows that inertial alignment is a general and thus important factor for the transport of atmospheric particles.