On the clustering of low-aspect-ratio oblate spheroids settling in ambient fluid

We have performed particle-resolved direct numerical simulations of many heavy non-spherical particles settling under gravity in the dilute regime. The are oblate spheroids aspect ratio $1.5$ and density . Two Galileo numbers considered, namely $111$ $152$ , for which a single spheroid follows steady vertical oblique path, respectively. In both cases, strongly inhomogeneous spatial distribution disperse phase form columnar clusters is observed, with significantly enhanced average velocity as consequence. Thus, contrast to previous results spheres, qualitative difference single-particle regime does not result qualitatively different behaviour many-particle cases. addition, we carried out an analysis pairwise interactions well-known drafting–kissing–tumbling set-up, spheres. varied systematically relative initial position between particle pair considered free-to-rotate rotationally locked ones. found that region attraction shapes, without rotation, very similar. However, significant differences occur during drafting tumbling phases. particular, spheres present longer phases separate quickly after collision. Spheroids remain close each other times collision, ones experience two or more collision events. Therefore, observed shape-induced increase interaction time might explain increased tendency cluster