Gravitational settling of two impermeable semi-torus particles

Abstract

This research aimed to numerically investigate the dynamics of two semi-torus particles using the Immersed Boundary (IB) method. Various initial configurations were considered: vertically aligned along the centre of the fluid channel (Case A), vertically aligned in an asymmetric location (Case B), and horizontally aligned symmetrically to the channel centreline (Case C). Additionally, the impact of different starting alignments on particle dynamics was explored. When the particles were dropped along the middle of the channel, their dynamics depended on the fluid viscosity. Higher viscosities led to drafting and kissing phases, while lower viscosities resulted in multiple cycles of drafting, kissing, and tumbling (DKT). Similarly, the dynamics of particles dropped from an asymmetric location were also influenced by viscosity. For horizontally aligned particles along the centreline, the obtained results agreed well with previous studies. Notably, the initial orientation of the particles had a significant effect on their behaviour, particularly in less viscous fluid conditions.