Effect of small density differences on the drafting-kissing-tumbling of oblate spheroidal particles

Particle-laden flows are common in nature and industry, often exhibiting complex collective dynamics. To explore particle-fluid interactions, studies frequently focus on a simplified two-particle configuration known as the drafting-kissing-tumbling (DKT) problem [1], typically with identical particles. However, real-world particles often differ slightly in size, shape, or density. Nie and Lin [2] showed that sedimentation of particles with different densities leads to richer dynamics, though their study was confined by walls. Here, we perform numerical simulations of DKT for two spheroidal particles with slightly different densities in an unbounded environment. The aspect ratio of the spheroid is 1.5 (oblate), the density ratio between the particle and the fluid will be varied in the range (1.5-2.0). The Galileo number is Ga=100, for which a single particle with the mentioned properties would follow a straight vertical path. We consider small differences in the density of the particles (of the order of one centesimal part of the fluid density), which results in a long-term, quasi-periodic behaviour with repeating DKT events.



[1] A. F. Fortes, D. D. Joseph, and T. S. Lundgren. J., Fluid Mech., 177:467–483, 1987.

[2] D. Nie and J. Lin. J., Fluid Mech., 896:A12, 2020.