丰水期珠江口黏性泥沙输运的三维数值模拟

3Dnumerical studyon cohesive sediment dynamics of the Pearl River Estuaryin the wet season

珠江口的黏性泥沙输运对区域海洋工程和河口海洋环境有着重要的影响。本文利用SELFE模型,针对珠江河口海域建立了一个采用非结构三角形网格的三维斜压水动力模型,可耦合模拟海流、潮流及风海流水动力环境,并在此基础上开发了包括底床模块的黏性泥沙输运模型。模拟结果与实测值验证较好,再现了丰水期珠江河口的泥沙输运特征以及最大浑浊带的变化和分布特点。研究表明,丰水期珠江口悬沙质量浓度西侧大于东侧,泥沙主要来自河口上游。河口浅滩上会形成最大浑浊带,最大质量浓度可达0.5g/L。珠江口最大浑浊带的形成主要受潮动力、重力环流及泥沙再悬浮和沉积过程影响,其中泥沙再悬浮和沉积过程对中滩的最大浑浊带影响显著,而重力环流作用对西滩的最大浑浊带影响显著。

The cohesive sediment dynamics have great potential engineering and environmental impacts in the Pearl River Estuary （PRE）.In this study,we established a 3D unstructured triangular grid hydrodynamics model by using the SELFE （Semi-implicit Eulerian-Lagrangian Finite Element） model for the PRE,considering the baroclinic current,tidal current and wind current.On the basis of the hydrodynamics model,we then developed a cohesive sediment model including a bed change module.From the numerical results which are in good agreement with the field data obtained in the wet season,the characteristics of turbidity maximum （TM） in the PRE can be well reproduced,and the relevant sediment dynamics can be explained.The results show that the suspended sediment concentration （SSC） in the west side is higher during the wet season,which indicates that the suspended sediment in the PRE is terrigenous.The TM is found in all ＂three shoals＂,and the suspended sediment concentration is up to 0.5 g/L.The tidal dynamics,gravitational circulation and sediment resuspension and deposition processes are the primary formation mechanisms of TM in the PRE.TM in the middle shoal is mainly caused by the sediment resuspension and deposition processes,on the other hand,the gravitational circulation is the predominant formation mechanisms of TM in the west shoal.