长江口潮流不对称时空分布特征

Spatial-temporal Characteristics of Tidal Current Asymmetry in the Yangtze River Estuary

河口地区的潮流不对称特性对近岸的泥沙输运、地貌改变有着很大的影响。但由于长期且高频的流速或流量数据较难获取,潮流不对称特性的研究较少。利用二维水动力数学模型,模拟长江大通以下感潮河段1 a的动力过程,研究长江口潮流不对称的时空分布规律。结合非稳态调和方法和偏度方法,分析长江口涨落潮流速不对称和涨落憩历时不对称趋势,并进一步分析长江口的粗、细颗粒泥沙运动趋势。研究结果表明:落憩历时更短,有利于细颗粒泥沙向陆运动;径流对落潮流流速的增强作用导致长江口落潮流速大于涨潮流速,有利于粗颗粒泥沙向海运动。研究成果对于明确长江口泥沙运动趋势及潮流不对称的影响有一定参考价值。

Tidal current asymmetry exerts evident impact on offshore sediment transport and topographical evolution in the estuary.However,due to the lack of long-term and high-frequency tidal velocity records,studies in this regard are insufficient.In this research,a two-dimensional numerical model is applied to simulate the tidal current in the Yangtze River Estuary.Non-stationary harmonic analysis together with the skewness method is applied to study the flow velocity asymmetry(FVA)and flow duration asymmetry(FDA),and further to reveal the transportation of suspended coarse and fine sediments.Results show that shorter duration of ebb current is favorable to the landward transport of fine sediments.Meanwhile,enhancement of the residual flow leads to larger ebb velocities,resulting in the seaward delivery of coarse sediments.