长江口北港口门海域悬沙输运机制分析  

Mechanisms on the suspended sediment transport in the mouth of North Channel of Yangtze River estuary

作　　者：陈景东[1] 汪亚平[1] 史本伟[1] 高建华[1] 杨世伦[2] 

机构地区：[1]南京大学地理与海洋科学学院 [2]华东师范大学河口海岸学国家重点实验室

出　　处：《海洋工程》2014年第3期45-54,共10页The Ocean Engineering

基　　金：国家重大科学研究计划资助项目(2013CB956502);国家自然科学基金重点资助项目(41130856);国家自然科学基金青年资助项目(40906042);河口海岸学国家重点实验室开放基金资助项目(SKLEC200906)

摘　　要：根据2012年10月24日至11月1日在长江口北港口门海域获取的沉积动力学数据,采用输运通量分解方法分析水沙输运机制。结果表明,长江口北港口门附近海域涨、落潮期间底部悬沙浓度与近底部流速呈显著线性相关,存在显著的再悬浮作用;潮周期内的悬沙输运具不对称特征,涨潮悬沙浓度大于落潮悬沙浓度,悬浮泥沙有向陆输运的趋势。拉格朗日平流输运是影响悬沙输运的主要贡献项;潮泵效应(尤其是潮汐捕捉效应)以及河口垂向环流作用是两个次要影响因素,在影响程度上前者比后者略大。观测发现,长江口北港口门海域潮流除了具有涨落潮流速、历时等不对称现象外,还具有流速结构不对称的特征,进而导致涨、落潮底部湍流混合程度不对称与输沙不对称,这可能是造成悬沙向河口内输运形成最大浑浊带的重要因素。Based on the hydrological observation at the entrance of North Channel of the Yangtze River estuary from October 24 to November 1,2012, the transport processes of water and suspended sediments were analyzed by the method of flux decomposition. The results showed that the suspended sediment concentration had a significant linear correlation with current speed in the bottom water layer during the flood and ebb tides, which indicated strong re-suspension events. The transport rate of suspended sediments was asymmetric with the suspended sediment concentration of flood tide being higher, which resuhed in a net onshore transport during the tidal cycle. The decomposing results showed that the Lagrangian advection transport played the leading role in suspended sediment flux, while the tidal pumping effect （especially the tidal trapping） and vertical circulation acted as the subordinate factors with the former prevailing over the latter. The field survey of this research revealed that in addition to the asymmetries in current velocity and duration, the vertical velocity structure also differed between flood and ebb tides, which induced the tidal asymmetries in the extent of turbulent mixing and net transport of suspended sediments. This might be the main factor in the formation of turbidity maximum in the Yangtze River estuary.

关 键 词：悬沙浓度 通量分解 再悬浮 平流输运 长江口 

分 类 号：TV148[水利工程—水力学及河流动力学]