Settling of chiral particles in a turbulent flow

Chiral particles are experimentally investigated while settling in water 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, and the turbulence strength varies between experiments in the range 0 less than or slanted equals italic Re Subscript lamda Baseline less than or slanted equals 250 <mml:math xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:mnf="http://cambridge.org/core/manifest" xmlns:cup="http://contentservices.cambridge.org" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:m="http://cambridge.org/core/metadata" xmlns:core="http://cambridge.org/core" xmlns:c="http://cambridge.org/core/content"> <mml:mn>0</mml:mn> <mml:mo>⩽</mml:mo> <mml:msub> <mml:mrow> <mml:mtext mathvariant="italic" class="MJX-tex-mathit">Re</mml:mtext> </mml:mrow> <mml:mi>λ</mml:mi> </mml:msub> <mml:mo>⩽</mml:mo> <mml:mn>250</mml:mn> </mml:math> $0 \leqslant \textit{Re}_\lambda \leqslant 250$ . Starting with quiescent particle settling, the chiral particle’s orientation dynamics is 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 weaken 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.