Coupled Rotation and Lateral Drift of a Helical Particle in Simple Shear Flow under Quasi-Equilibrium Conditions

Helical particles are prevalent in both nature and scientific studies; however, the intricate dynamics resulting from their helical shapes remain not fully understood. Utilizing a high-fidelity numerical approach grounded in the lattice Boltzmann method, we conducted a comprehensive investigation into the motion characteristics of helical particles in a simple shear flow under conditions of weak inertia, specifically at a Reynolds number of 0.1. These helical particles were created by twisting rectangular particles around their longest principal axis. In a quasi-equilibrium state, where one principal axis is parallel to the flow vorticity axis, the particle motion exhibited two distinct modes: rotation around the vorticity axis and lateral drift along it. Two scenarios were examined: one where the particle's twisting axis was aligned with the vorticity axis, and the other where a non-twisting axis was aligned with the vorticity axis. It was found that within the parameter range considered, the rotation and lateral drift of the particles were interlinked. Both follow their respective sine functions of the rotation angle, achieving their maximum and minimum values when the particles are either aligned with the flow direction or oriented perpendicular to it. The change in the particle’s twist angle causes the amplitudes of oscillations in rotational angular velocity and lateral drift velocity to exhibit periodic variations. Several regime diagrams for various quasi-equilibrium states were presented, offering insights into the dynamic characteristics of helical objects in complex flows.