Dynamics of an elliptical cylinder in confined Poiseuille flow

Flows of solid particles in suspension are ubiquitous in both nature and industry. Compared to a spherical particle, the dynamics of a non-spherical particle in flow is much less understood, especially its interaction with a micro-confined environment. We consider an elliptical particle because its different aspect ratios can represent a large family of non-spherical shapes. To capture the complex dynamic interface between the particle and the flow, we employ the smoothed particle hydrodynamics method and benefit from its Lagrangian property. In particular, we consider an elliptical cylinder in confined Poiseuille flow and systematically study the effects of five factors: the confinement strengths, the particle Reynolds numbers between 0.1 and 10, particle initial positions/orientations, and the particle aspect ratios, respectively. We identify three types of periodic motion at steady state and they are tumbling, oscillation with either major or mini axis along the flow. In weakly confined channels, the particle always tumbles and has determined focusing positions off the centerlines, which depend mainly on the competition between the shear gradient lift and wall-induced force in the transverse direction. In strongly confined channels, the particle has steady oscillations at the centerlines, and its actual state depends on the Reynolds number, initial states, and aspect ratios of the particle. Our study provides a valuable insight into the dynamics of non-spherical particles in microfluidic systems.