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| Simulation of the impacts of varying junction angles and flow ratios on microplastic transport in confluences |
| CAO Li-wei1, SHEN Yu-han1,2, GAO Wei-zheng1, LI De-hong1, LI Xiao-long1, LI Sheng1 |
1. College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China;
2. Key Laboratory of Agricultural Water and Soil Engineering in Arid Regions, Ministry of Education, Northwest Agriculture & Forestry University, Yangling 712100, China |
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Abstract Microplastics exhibited unique properties and possessed a wide distribution across various environments. The confluence served as a key point for the contamination of microplastics. At present, there was a lack of effective methods to reveal the motion characteristics and accumulation areas of microplastics at the confluence. The motion and fate of microplastics should be accurately captured at the confluence. The three-dimensional hydrodynamic-microplastic transport model for microplastics was established at the confluence. The transport mechanism and fate of microplastics were investigated under varying junction angles and flow ratios through the coupled CFD-DEM method. The results showed that (1) The low velocity zones, including the flow separation, flow stagnation, and downstream of the flow separation, would evolve into regions of microplastic accumulation. (2) Microplastics were primarily influenced by the vortex located in the flow separation, entering the vortex zone from the right bank of the mainstream and gradually forming an elliptical enrichment region. (3) The concentrations of microplastics in the center of the flow separation were positively correlated with the junction angles. (4) There was a linear negative correlation between the concentrations of microplastics and the flow ratios in the center of the flow separation, R2=0.9007. The number of microplastics in the flow separation exhibited a significant negative correlation with the flow ratio at the confluence. The findings of the study would advance the fundamental understanding of microplastic motion in confluences and establish a theoretical framework for precise prevention and control strategies against microplastic pollution.
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Received: 19 June 2024
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