数值分析长江口深水航道上段淤积的原因

Numerical analysis of the sediment deposition in the upper reach of the deepwater navigation channel in the Changjiang River Estuary

目前,长江口北槽深水航道上段淤积较为严重,对航运产生了不利的影响。本文利用Delft3D-FLOW建立了长江口二维潮流的数学模型,并利用实测潮位、流速及流向资料对模型进行了率定和验证,模型计算结果与实测数据符合较好,该模型较好地反应了深水航道工程后长江口的水动力情况。根据模型计算结果,特别是南、北槽上河段主河道流速沿程变化过程、横沙通道涨落潮流量、南北槽分流比,对北槽深水航道上段淤积原因进行了分析,北槽沿程流速远小于南槽沿程流速,尤其横沙通道以上北槽河段流速更小,而且横沙通道涨、落潮量均较大,削弱了北槽和南港之间的水体交换,从而加强了泥沙在北槽深水航道上段进口段的落淤。

At present, the upper reach of the Deepwater Navigation Channel in the Changjiang River Estuary is silted heavily, which brings negative influences on navigation. A two-dimensional numerical model is set up to simulate the hydrodynamics of the Changjiang River Estuary with Delfl3D-FLOW in this paper. This model has been calibrated and validated with the observed tidal level, flow velocity magnitude and direction, and the computed results agree well with the observed data, which also shows the model can well simulate the hydrodynamics of the Changjiang River Estuary caused by the Deepwater Navigation Channel Project. Based on the analysis of computed results, especially the velocity along the South Passage andNorth Passage, the flood and ebb flow in the Hengsha Passage, and the flow spilt ratio of South Passage and North Passage, it presents that one main reason for the sediment deposition in the upper reach of the Deepwater Navigation Channel is that the velocity along the North Passage is far less than that along South Passage, above all, the velocity in North Passage upstream of the Hengsha Passage is even smaller; another reason is that the flood and ebb flow of Hengsha Passage are large, which weakens the water exchange between the North Passage and South Channel.