Author(s): Arefeh Shamskhany; Shooka Karimpour

Linked Author(s): Shooka Karimpour

Keywords: Microplastic pollution; Sediment transport; Stokes number; Settling velocity; Vortex trapping

Abstract: The drastic increase in global plastic production has resulted in a proportional upsurge in Microplastic (MP) input to the aquatic environment. MP pollution has detrimental effects on aquatic ecosystem health. Understanding the transport and distribution of these aquatic contaminants can help future pollution mitigation. MPs have diverse physical characteristics due to their different origins and exposure to weathering processes. Additionally, transport mechanisms such as biofouling and turbulent mixing can alter the gravity-driven transport of MPs. Here we used a hybrid Lagrangian-Eulerian model to investigate the entrainment and transport of MPs in a fully-developed turbulent flow induced over the Backward-Facing Step. We employed the particle Reynolds number, settling parameter, and the Stokes number to characterize the distinct transport and entrainment of MPs of different sizes, densities, and shapes in the turbulent flow. Based on the results of this study, reducing the particle size and the marginal density results in the Stokesian regime and a lower range of Stokes number, which is associated with the more prominent drag effect. Therefore, as the particle Reynolds number and the range of Stokes number decrease, particle motions become less gravitational. On the other hand, non-spherical shapes with high surface area-to-volume ratios, such as fibres and films, are associated with lower particle Reynolds numbers and Stokes numbers. Our results reveal that when the range of Stokes number is small, MPs gravity-induced motion can be easily altered by the drag force and therefore, particles are transported with the ambient flow to farther downstream locations.

DOI: https://doi.org/10.3850/978-90-833476-1-5_iahr40wc-p0497-cd

Year: 2023