The settlement of non-spherical particles, such as propagules of plants and natural sediments, are commonly observed in riverine ecosystems. The settling process is influenced by both particle properties (size, density and shape) and fluid properties (density and viscosity). Therefore, the drag law of non-spherical particles is a function of both particle Reynolds number and particle shape. Herein, a total of 828 settling data are collected from the literatures, which cover a wide range of particle Reynolds number (0.008–10000). To characterize the influence of particle shapes, sphericity is adopted as the general shape factor, which varies from 0.421 to 1.0. By comparing the measured drag with the standard drag curve of spheres, we modify the spherical drag law with three shape-dependent functions to develop a new drag law for non-spherical particles. Combined with an iterative procedure, a new model is thus obtained to predict the settling velocity of non-spherical particles of various shapes and materials. Further applications in hydrochorous propagule dispersal and sediment transport are projected based on deeper understanding of the settling process.

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Posted 16 Mar, 2021
Received 16 Mar, 2021
Invitations sent on 14 Mar, 2021
On 23 Feb, 2021
On 22 Feb, 2021
Posted 16 Mar, 2021
Received 16 Mar, 2021
Invitations sent on 14 Mar, 2021
On 23 Feb, 2021
On 22 Feb, 2021
The settlement of non-spherical particles, such as propagules of plants and natural sediments, are commonly observed in riverine ecosystems. The settling process is influenced by both particle properties (size, density and shape) and fluid properties (density and viscosity). Therefore, the drag law of non-spherical particles is a function of both particle Reynolds number and particle shape. Herein, a total of 828 settling data are collected from the literatures, which cover a wide range of particle Reynolds number (0.008–10000). To characterize the influence of particle shapes, sphericity is adopted as the general shape factor, which varies from 0.421 to 1.0. By comparing the measured drag with the standard drag curve of spheres, we modify the spherical drag law with three shape-dependent functions to develop a new drag law for non-spherical particles. Combined with an iterative procedure, a new model is thus obtained to predict the settling velocity of non-spherical particles of various shapes and materials. Further applications in hydrochorous propagule dispersal and sediment transport are projected based on deeper understanding of the settling process.

Figure 1

Figure 2

Figure 3

Figure 4
The full text of this article is available to read as a PDF.
This is a list of supplementary files associated with this preprint. Click to download.
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