Topology-driven hydrodynamic interactions in suspensions of ring-shaped particles

Abstract

Abstract Content of image described in text. We explored the collective sedimentation of non-convex ring-shaped particles in viscous suspensions using direct numerical simulations based on the smoothed profile method. The toroidal particle geometry introduces an internal flow pathway that allows fluid penetration, fundamentally altering disturbance–flow interactions relative to convex particles. Simulations are performed at italic Re equals 0.1 Re=0.1 $\textit{Re}=0.1$ over volume fractions 0.001 less than or equals phi less than or equals 0.1 0.001≤ϕ≤0.1 $0.001 \le \phi \le 0.1$ . For an isolated particle, the drag coefficient scales with Stokes law but remains systematically larger than that of convex particles, consistent with enhanced viscous dissipation associated with flow penetrating through the ring opening. In suspensions, the mean settling velocity exhibits enhanced hindered settling, following a Richardson–Zaki-type scaling with exponent n almost equals 7 n≈7 $n \approx 7$ . Velocity fluctuations display anisotropic behaviour and follow a phi Superscript 1 divided by 3 ϕ1/3 $\phi ^{1/3}$ scaling in dilute regimes, consistent with hydrodynamic screening governed by a finite correlation length. Spatial correlations and correlation times reveal persistent streamwise coherence associated with gravity-aligned wake interactions, while the suspension microstructure exhibits multiple preferred separation distances imposed by the ring topology. The results show that particle topology, beyond conventional shape descriptors, constitutes a key control parameter governing hydrodynamic interactions, microstructure, and transport in particulate suspensions.