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A numerical study of the settling of non-spherical particles in quiescent water

Xiaoyong Cheng Orcid Logo, Zhixian Cao Orcid Logo, Ji Li Orcid Logo, Alistair Borthwick Orcid Logo

Physics of Fluids, Volume: 35, Issue: 9

Swansea University Author: Ji Li Orcid Logo

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DOI (Published version): 10.1063/5.0165555

Abstract

Settling of non-spherical particles is poorly understood with previous studies having focused mainly on spherical particles. Here, a series of particle-resolved direct numerical simulations are conducted using FLOW-3D (commercial computational fluid dynamics software) for spheres and five regular, n...

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Published in: Physics of Fluids
ISSN: 1070-6631 1089-7666
Published: AIP Publishing 2023
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URI: https://cronfa.swan.ac.uk/Record/cronfa64684
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spelling v2 64684 2023-10-10 A numerical study of the settling of non-spherical particles in quiescent water 4123c4ddbcd6e77f580974c661461c7c 0000-0003-4328-3197 Ji Li Ji Li true false 2023-10-10 CIVL Settling of non-spherical particles is poorly understood with previous studies having focused mainly on spherical particles. Here, a series of particle-resolved direct numerical simulations are conducted using FLOW-3D (commercial computational fluid dynamics software) for spheres and five regular, non-spherical shapes of sediment particles, i.e., prolate spheroid, oblate spheroid, cylinder, disk, and cube. The Galileo number varies from 0.248 to 360, and the particle Reynolds number Rep ranges from 0.002 77 to 562. The results show that a non-spherical particle may experience larger drag and, consequently, attain a lower terminal velocity than an equivalent sphere. If Rep is sufficiently small, the terminal velocity is less affected by particle shape as characterized by the particle aspect ratio. For relatively large Rep⁠, the shape effect (represented by the Corey shape factor) becomes more significant. Empirical correlations are derived for the dimensionless characteristic time t95∗ and displacement s95∗ of particle settling, which show that t95∗ remains constant in the Stokes regime (⁠ Rep < 1) and decreases with increasing Rep in the intermediate regime (1 ≤ Rep < 103), whereas s95∗ increases progressively with increasing Rep over the simulated range. It is also found that in the Stokes regime, particle orientation remains essentially unchanged during settling, and so the terminal velocity is governed by the initial orientation. In the intermediate regime, a particle provisionally settling at an unstable orientation self-readjusts to a stable equilibrium state, such that the effect of initial orientation on the terminal velocity is negligible. Moreover, an unstable initial orientation can enhance the vertical displacement and may promote vortex shedding. Journal Article Physics of Fluids 35 9 AIP Publishing 1070-6631 1089-7666 Gravitational force, Computational fluid dynamics, Fluid drag, Vortex dynamics 20 9 2023 2023-09-20 10.1063/5.0165555 http://dx.doi.org/10.1063/5.0165555 COLLEGE NANME Civil Engineering COLLEGE CODE CIVL Swansea University This work was financially supported by the National Natural Science Foundation of China (Grant No. 52239007). 2023-11-07T15:20:14.3861694 2023-10-10T08:50:10.4342162 Faculty of Science and Engineering School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Civil Engineering Xiaoyong Cheng 0009-0003-2472-5655 1 Zhixian Cao 0000-0001-5161-385x 2 Ji Li 0000-0003-4328-3197 3 Alistair Borthwick 0000-0001-6053-7764 4 64684__28746__1a8406014e5440abbd14c92c1e83fcf7.pdf POF23-AR-04793.pdf 2023-10-10T09:21:36.8818471 Output 5565223 application/pdf Accepted Manuscript true Author accepted manuscript document released under the terms of a Creative Commons CC-BY licence using the Swansea University Research Publications Policy. true eng https://creativecommons.org/licenses/by/4.0/
title A numerical study of the settling of non-spherical particles in quiescent water
spellingShingle A numerical study of the settling of non-spherical particles in quiescent water
Ji Li
title_short A numerical study of the settling of non-spherical particles in quiescent water
title_full A numerical study of the settling of non-spherical particles in quiescent water
title_fullStr A numerical study of the settling of non-spherical particles in quiescent water
title_full_unstemmed A numerical study of the settling of non-spherical particles in quiescent water
title_sort A numerical study of the settling of non-spherical particles in quiescent water
author_id_str_mv 4123c4ddbcd6e77f580974c661461c7c
author_id_fullname_str_mv 4123c4ddbcd6e77f580974c661461c7c_***_Ji Li
author Ji Li
author2 Xiaoyong Cheng
Zhixian Cao
Ji Li
Alistair Borthwick
format Journal article
container_title Physics of Fluids
container_volume 35
container_issue 9
publishDate 2023
institution Swansea University
issn 1070-6631
1089-7666
doi_str_mv 10.1063/5.0165555
publisher AIP Publishing
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Civil Engineering{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Aerospace, Civil, Electrical, General and Mechanical Engineering - Civil Engineering
url http://dx.doi.org/10.1063/5.0165555
document_store_str 1
active_str 0
description Settling of non-spherical particles is poorly understood with previous studies having focused mainly on spherical particles. Here, a series of particle-resolved direct numerical simulations are conducted using FLOW-3D (commercial computational fluid dynamics software) for spheres and five regular, non-spherical shapes of sediment particles, i.e., prolate spheroid, oblate spheroid, cylinder, disk, and cube. The Galileo number varies from 0.248 to 360, and the particle Reynolds number Rep ranges from 0.002 77 to 562. The results show that a non-spherical particle may experience larger drag and, consequently, attain a lower terminal velocity than an equivalent sphere. If Rep is sufficiently small, the terminal velocity is less affected by particle shape as characterized by the particle aspect ratio. For relatively large Rep⁠, the shape effect (represented by the Corey shape factor) becomes more significant. Empirical correlations are derived for the dimensionless characteristic time t95∗ and displacement s95∗ of particle settling, which show that t95∗ remains constant in the Stokes regime (⁠ Rep < 1) and decreases with increasing Rep in the intermediate regime (1 ≤ Rep < 103), whereas s95∗ increases progressively with increasing Rep over the simulated range. It is also found that in the Stokes regime, particle orientation remains essentially unchanged during settling, and so the terminal velocity is governed by the initial orientation. In the intermediate regime, a particle provisionally settling at an unstable orientation self-readjusts to a stable equilibrium state, such that the effect of initial orientation on the terminal velocity is negligible. Moreover, an unstable initial orientation can enhance the vertical displacement and may promote vortex shedding.
published_date 2023-09-20T15:20:18Z
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