On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid
Abstract
We have performed particle-resolved direct numerical simulations of many heavy non-spherical particles settling under gravity in the dilute regime. The particles are oblate spheroids of aspect ratio $1.5$ and density ratio $1.5$ . Two Galileo numbers are considered, namely $111$ and $152$ , for which a single oblate spheroid follows a steady vertical and a steady oblique path, respectively. In both cases, a strongly inhomogeneous spatial distribution of the disperse phase in the form of columnar clusters is observed, with a significantly enhanced average settling velocity as a consequence. Thus, in contrast to previous results for spheres, the qualitative difference in the single-particle regime does not result in a qualitatively different behaviour of the many-particle cases. In addition, we have carried out an analysis of pairwise interactions of particles in the well-known drafting–kissing–tumbling set-up, for oblate spheroids of aspect ratio $1.5$ and for spheres. We have varied systematically the relative initial position between the particle pair and we have considered free-to-rotate particles and rotationally locked ones. We have found that the region of attraction for both particle shapes, with and without rotation, is very similar. However, significant differences occur during the drafting and tumbling phases. In particular, free-to-rotate spheres present longer drafting phases and separate quickly after the collision. Spheroids remain close to each other for longer times after the collision, and free-to-rotate ones experience two or more collision events. Therefore, we have observed a shape-induced increase in the interaction time which might explain the increased tendency to cluster of the many-particle cases.
Related
- Orientation and slip statistics of spheroids settling in turbulence
- On the settling of a spherical particle in slightly perturbed ambient fluid
- Perturbation Theory for Translating Oblate-Spheroidal Droplets with Internal Circulation
- Implications of an analysis of the shear transformation of a zone of an oblate spheroid for dislocation theory, grain boundary sliding and superplasticity
- Rapid fabrication of height-tunable high-aspect-ratio voxels by tailored Bessel beams
BibTeX
@article{moriche2026clustering,
title = {{On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid}},
author = {Manuel Moriche and Daniel Hettmann and Manuel García-Villalba and Markus Uhlmann},
journal = {Journal of Fluid Mechanics},
year = {2026},
month = oct,
doi = {10.1017/jfm.2023.261},
eprint = {2303.12075},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05781414v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid
AU - Manuel Moriche
AU - Daniel Hettmann
AU - Manuel García-Villalba
AU - Markus Uhlmann
PY - 2026
DA - 2026/10/06
JO - Journal of Fluid Mechanics
DO - 10.1017/jfm.2023.261
UR - https://hal.science/hal-05781414v1
AB - We have performed particle-resolved direct numerical simulations of many heavy non-spherical particles settling under gravity in the dilute regime. The particles are oblate spheroids of aspect ratio $1.5$ and density ratio $1.5$ . Two Galileo numbers are considered, namely $111$ and $152$ , for which a single oblate spheroid follows a steady vertical and a steady oblique path, respectively. In both cases, a strongly inhomogeneous spatial distribution of the disperse phase in the form of columnar clusters is observed, with a significantly enhanced average settling velocity as a consequence. Thus, in contrast to previous results for spheres, the qualitative difference in the single-particle regime does not result in a qualitatively different behaviour of the many-particle cases. In addition, we have carried out an analysis of pairwise interactions of particles in the well-known drafting–kissing–tumbling set-up, for oblate spheroids of aspect ratio $1.5$ and for spheres. We have varied systematically the relative initial position between the particle pair and we have considered free-to-rotate particles and rotationally locked ones. We have found that the region of attraction for both particle shapes, with and without rotation, is very similar. However, significant differences occur during the drafting and tumbling phases. In particular, free-to-rotate spheres present longer drafting phases and separate quickly after the collision. Spheroids remain close to each other for longer times after the collision, and free-to-rotate ones experience two or more collision events. Therefore, we have observed a shape-induced increase in the interaction time which might explain the increased tendency to cluster of the many-particle cases.
SN - 0022-1120
SN - 1469-7645
ER -