Settling of chiral particles in a turbulent flow

TL;DR

This study investigates how chiral particles settle in turbulent water flows, revealing their orientation behaviors, settling modes, and the influence of turbulence on their dynamics through experiments and a theoretical model.

Contribution

It provides new insights into the settling behavior of chiral particles in turbulence, combining experimental observations with a theoretical model to explain different settling modes.

Findings

Chiral particles exhibit preferred orientations and strong coupling between translation and rotation.

Turbulence reduces the alignment and rotation-translation coupling of particles.

Multiple settling modes are identified, characterized by rotation angle evolution.

Abstract

Chiral particles are experimentally investigated while settling inwater with various turbulence intensity levels. The locations and orientations of the particles are tracked over time, allowing the close investigation of the particles' settling dynamics. The generated turbulent flow is measured using laser Doppler anemometry (LDA), and the turbulence strength varies between experiments in the range $0 \leq Re_\lambda \leq 250$. Starting with quiescent particle settling, the chiral particle's orientation dynamics are studied, revealing a preferred alignment and a strong translation-rotation coupling. The particle chirality determines the preferred rotation direction, though the alignment and translation-rotation coupling gradually vanish with increasing turbulence. We identify multiple settling modes for the chiral particles, which are characterised by the evolution of the rotation angles. Finally, a theoretical model assuming a simplified chiral particle in Stokes flow clarifies the emergence of each settling mode.