Hydrodynamic Behavior of Non-spherical Particles in Confined Vertical Flows: A Resolved CFD-DEM Study

TL;DR

This study uses CFD-DEM simulations to analyze how irregular non-spherical particles, like polymetallic nodules, behave in vertical flows, revealing shape effects on drag, velocity, and transport regimes.

Contribution

It provides detailed insights into shape-induced drag enhancement and flow regime transitions for non-spherical particles in confined vertical flows, extending understanding beyond spherical models.

Findings

Shape increases drag by 2.0-2.3 times compared to spheres.

Vertical transport transitions from intermittent to stable convection.

Large particles show non-monotonic drag variance behavior.

Abstract

We investigate the sedimentation and vertical hydraulic transport of irregular polymetallic nodules (PMNs) using resolved CFD-DEM with multisphere particles spanning $100 < Re_p < 3000$. Shape effects induce 2.0-2.3 times drag enhancement relative to volume-equivalent spheres, arising from 50\% larger frontal areas and wake asymmetry, reducing terminal velocities by 29-33\%. Vertical transport exhibits velocity-driven transitions from intermittent settling to stable convection, as demonstrated by residence-time and drag-force statistics. While PMNs exhibit enhanced rotational-translational coupling and broader force fluctuations, the regime progression qualitatively resembles that of volume-equivalent spherical particles. Drag variance evolution reveals contrasting behavior: small particles $(d/D=0.082)$ show narrow distributions and wake suppression at higher velocities, while large particles $(d/D=0.22)$ exhibit non-monotonic variance. These findings elucidate shape-confinement interactions in vertical transport and establish bounds on the applicability of volume-equivalent spherical particles in reduced-order models.