Modelling the Effects of Multiple Fractal Dimensions on the Flocculation and Resuspension Processes of Cohesive Sediment
Modelling the Effects of Multiple Fractal Dimensions on the Flocculation and Resuspension Processes of Cohesive Sediment
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多重分形维数对粘性沉积物絮凝和再悬浮过程影响的模拟
DOI：
10.3389/fmars.2021.746630
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
Chunyang Xu;A. Cuthbertson;Yan Zhou;P. Dong;Yongping Chen
中科院分区：
文献类型：
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作者：
Chunyang Xu;A. Cuthbertson;Yan Zhou;P. Dong;Yongping Chen
粘性沉积物的絮凝是海岸沉积物输运中的一个关键过程，其在数值模型中的适当表示对于污染物输运、海岸形态动力学和工程问题的预测至关重要。在这项研究中，絮凝模型考虑到多个分形维数的影响被纳入到一个两阶段的数值模拟框架，并用于调查的影响，时空变化的泥沙浓度的时间演变的局部絮凝体的大小。首先，该模型被应用到模拟的粘土悬浮液在垂直的网格搅拌沉降柱的聚集，结果证实了多个分形维数的重要性时，预测絮凝体尺寸的时间演变。特别是采用多个分形维数，使得两相数值模型能够更好地匹配测得的沉降柱数据，并改善整体相关性。这是特别的情况下，当絮凝物倾向于更迅速地调整到其平衡尺寸时，在沉降的早期预测初始絮凝物尺寸的增长。两相模型，然后应用于模拟潮汐驱动的渠道中的泥浆再悬浮过程的现场测量。再次，通过考虑多个分形维数内的絮凝模型，更好的协议之间获得观测和模拟悬浮泥沙浓度，而预测的絮凝体大小也一般雅阁与以前的现场测量在同一河口。
The flocculation of cohesive sediments represents a critical process in coastal sediment transport, with its appropriate representation in numerical models crucial for the prediction of contaminant transport, coastal morphodynamics and engineering problems. In this study, a flocculation model considering the effects of multiple fractal dimensions is incorporated into a two-phase numerical modelling framework and used to investigate the effects of spatio-temporal variations in sediment concentrations on the temporal evolution of local floc sizes. Initially, the model is applied to simulate the aggregation of clay suspensions in a vertical grid-stirred settling column, with results confirming the importance of multiple fractal dimensions when predicting the time evolution of floc sizes. The adoption of multiple fractal dimensions, in particular, allows the two-phase numerical model to better match the measured settling column data with improved overall correlation. This is especially the case when predicting initial floc size growth during the early period of settling when the flocs tend to adjust more rapidly to their equilibrium sizes. The two-phase model is then applied to simulate field measurements of mud resuspension process in a tidally driven channel. Again, by considering multiple fractal dimensions within the flocculation model, better agreement is obtained between observed and modelled suspended sediment concentrations, while predicted floc sizes are also in general accord with previous field measurements made within the same estuary.