Triaxial Asymmetry Driven Rotational Dynamics and Lateral Equilibrium Position in Inertial Flow

TL;DR

This study investigates how geometric asymmetry in triaxial particles influences their rotational behavior and lateral migration in inertial flow, revealing new dynamics governed by particle shape and inertia effects.

Contribution

It introduces a generalized Jeffery equation accounting for moment-of-inertia effects and links particle asymmetry to flow-induced rotation and migration behaviors.

Findings

Asymmetry governs particle orientation and migration.

A scalar offset from Jeffery's orbit quantifies rotational deviations.

Gyration diameter predicts lateral equilibrium position.

Abstract

The growing use of triaxial particles in microfluidic, microrobotic, and biological systems makes it essential to understand how their rotational dynamics couples with lateral migration in microscale flows. Our experiments in inertial Poiseuille flow reveal that geometric asymmetry in triaxial, multifaceted disks governs their orientation, migration, and rotational period, distinguishing them from classical axisymmetric objects. We identified a Reynolds- and geometry-dependent shift in preferred rotational orientation, arising from the Dzhanibekov effect, with transition modes determined by the particle's principal-axis configuration. We quantified a scalar offset from Jeffery's orbit prediction and introduced a fitting parameter that generalizes the Jeffery equation to include moment-of-inertia effects on rotational dynamics. Finally, we report the diameter of gyration as a predictor of the lateral equilibrium position of inertially focused triaxial particles. Our results link particle asymmetry to migration and rotation in flow, expanding our understanding of particle dynamics.