长江口北槽深水航道水沙输运特征三维数值模拟

基于长江口北槽实测水文观测资料,利用三维水流泥沙数学模型对北槽内盐水楔、水流及泥沙输运特征等进行模拟分析。结果表明:北槽中段泥沙表、底层差异明显,垂向分布不均匀,受盐水楔影响,泥沙更容易在中段聚集;泥沙北槽内输运距离较长,1个落潮过程难以输出北槽,在反复输移中跨越航槽几率大大增加,尤其北槽中下段涨转落低流速时段较长,底部含沙量较高,易形成航道回淤;输出北槽的部分泥沙水体可能在旋转流作用下经九段沙及南导堤重新回到北槽,累积循环,成为北槽内含沙量较高的重要原因。

3D numerical simulation on water and sediment transport characteristics in the Yangtze Estuary deepwater channel

Based on hydrological observation data in the North Passage of the Yangtze River,we apply three-dimensional numerical model to simulate saline wedge,water current,and sediment transportation.The results show that obvious differences exist between the sediment of surface and bottom layer,and the distribution of sediment is uneven vertically.Sediment is more likely to concentrate in the middle North Passage,due to saline wedge.At the same time,the distance from the upper North Passage to open seas is so long,that sediment could hardly be transported out of the North Passage during an ebb-tidal duration,which greatly increases the possibility for the sediment to transport cross the waterway.Especially,high-concentration sediment often silts in waterway when current changes direction with low velocity and long duration in the middle and lower North Passage.Even after the sediment is transported out of the North Passage,rotary current may carry part of the sediment back to the North Passage through Jiuduansha wetland and south jetty.This transport pattern happens repeatedly,which contributes to high sediment concentration in the North Passage.