Inertia induces strong orientation fluctuations of non-spherical atmospheric particles

TL;DR

This paper demonstrates that inertia causes strong, oscillatory orientation fluctuations in non-spherical atmospheric particles like volcanic ash and ice crystals, affecting their atmospheric behavior and radiative properties.

Contribution

It provides experimental and theoretical evidence that inertia induces oscillations in particle orientation, highlighting the importance of accounting for this effect in atmospheric models.

Findings

Orientation oscillations observed in spheroids settling in air

Oscillations decay over time, unlike in liquids

Inertia due to density ratio causes these effects

Abstract

The orientation of non-spherical particles in the atmosphere, such as volcanic ash and ice crystals, influences their residence times, and the radiative properties of the atmosphere. Here, we demonstrate experimentally that the orientation of heavy submillimeter spheroids settling in still air exhibits decaying oscillations, whereas it relaxes monotonically in liquids. Theoretical analysis shows that these oscillations are due to particle inertia, caused by the large particle-fluid mass-density ratio. This effect must be accounted for to model solid particles in the atmosphere.