Sedimentation of inertial monodisperse suspensions of cubes and spheres

Ahmadi, Arman; Wachs, Anthony

doi:10.1103/physrevfluids.6.044306

Cited by 13 publications

(6 citation statements)

References 77 publications

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“…Richardson and Zaki (1954) proposed a simple correlation that is widely used: microstructure for 𝜙 = 20%. A similar tendency for horizontal particle alignment at moderate concentrations and an isotropic particle distribution for the dense regime was observed in later studies (Zaidi et al, 2014;Hamid et al, 2014;Willen and Prosperetti, 2019;Seyed-Ahmadi and Wachs, 2021).…”

Section: Introductionsupporting

confidence: 86%

Inertial Effects in Sedimenting Suspensions of Solid Spheres in a Liquid

Shajahan

Breugem

2023

Preprint

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Section: Introductionsupporting

confidence: 86%

Inertial Effects in Sedimenting Suspensions of Solid Spheres in a Liquid

Shajahan

Breugem

2023

Preprint

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“…(2016 b ) and Ardekani et al. (2016) for spheroids, and to that of Seyed-Ahmadi & Wachs (2021) for cubes. We have selected this definition over the one used in some works dealing exclusively with spheroids (Zhou et al.…”

Section: Problem Descriptionmentioning

confidence: 76%

“…Turning now to other shapes, Seyed-Ahmadi & Wachs (2021) more recently studied the behaviour of settling cubes with , and Galileo numbers for which a single cube tends to a steady oblique path with very small tilting angle () and to a helical path () for large times. For their smallest solid volume fraction these authors report an increase in the relative settling velocity, which is similar to what is observed in suspensions of spheres (cf.…”

Section: Introductionmentioning

confidence: 99%

“…figure 2). Interestingly, Seyed-Ahmadi & Wachs (2021) observe that the intensity of columnar cluster formation (measured with the aid of particle-pair distribution functions) is somewhat lower in the case of cubes as compared with the spherical counterpart. This effect is attributed by the authors to higher rotation rates in the former case, leading to an enhanced lift force that increases their probability to escape from an existing cluster.…”

Section: Introductionmentioning

confidence: 99%

“…The authors suggest that the onset of clustering in dilute suspensions of spherical particles is triggered by the bifurcation of the wake flow from steady axisymmetric to steady oblique, with the consequence that the particles in the latter case drift horizontally (with random azimuthal angle) leading to an enhanced probability of particle-particle encounters. Further data on collective effects upon clustering are available from the PR-DNS studies of Zaidi, Tsuji & Tanaka (2014), Fornari, Picano & Brandt (2016a) and Seyed-Ahmadi & Wachs (2021), which were all performed in similar triply periodic configurations, and from the work of Huisman et al (2016), who conducted experiments in a settling column with glass beads in water. An overview of the average settling velocities from these various datasets for dilute suspensions of spherical particles in an otherwise ambient fluid is given in figure 2.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

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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.

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