AbstractThis study investigates the longitudinal variation of lateral entrapment of suspended sediment, as is o'/> Longitudinal variation in lateral trapping of fine sediment in tidal estuaries: observations and a 3D exploratory model
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Longitudinal variation in lateral trapping of fine sediment in tidal estuaries: observations and a 3D exploratory model

机译：潮汐河口细沙横向捕获的纵向变化：观测和3D探索模型

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AbstractThis study investigates the longitudinal variation of lateral entrapment of suspended sediment, as is observed in some tidal estuaries. In particular, field data from the Yangtze Estuary are analysed, which reveal that in one cross-section, two maxima of suspended sediment concentration (SSC) occur close to the south and north sides, while in a cross-section 2 km down-estuary, only one SSC maximum on the south side is present. This pattern is found during both spring tide and neap tide, which are characterised by different intensities of turbulence. To understand longitudinal variation in lateral trapping of sediment, results of a new three-dimensional exploratory model are analysed. The hydrodynamic part contains residual flow due to fresh water input, density gradients and Coriolis force and due to channel curvature-induced leakage. Moreover, the model includes a spatially varying eddy viscosity that accounts for variation of intensity of turbulence over the spring-neap cycle. By imposing morphodynamic equilibrium, the two-dimensional distribution of sediment in the domain is obtained analytically by a novel procedure. Results reveal that the occurrence of the SSC maxima near the south side of both cross-sections is due to sediment entrapment by lateral density gradients, while the second SSC maximum near the north side of the first cross-section is by sediment transport due to curvature-induced leakage. Coriolis deflection of longitudinal flow also contributes the trapping of sediment near the north side. This mechanism is important in the upper estuary, where the flow due to lateral density gradients is weak.
机译： 摘要 该研究调查了悬浮沉积物的侧向包裹性的纵向变化在一些潮汐河口。特别是，对长江口的实地数据进行了分析，结果表明，在一个断面中，两个最大的悬浮沉积物浓度（SSC）出现在南侧和北侧附近，而在断面下2公里处，南侧最多只能有一个SSC。这种模式在春季和春季潮汐中都发现，其特征是湍流强度不同。为了了解沉积物的侧向捕集的纵向变化，分析了新的三维探索模型的结果。由于新鲜水输入，密度梯度和科里奥利力以及由于通道曲率引起的泄漏，流体动力学部分包含剩余流量。此外，该模型包括一个空间变化的涡流粘度，该涡流粘度可解释在春季-午睡周期内湍流强度的变化。通过施加形态动力学平衡，通过一种新颖的方法解析地获得了该区域内沉积物的二维分布。结果表明，两个横截面南侧附近SSC最大值的发生是由于侧向密度梯度导致的泥沙截留，而第一个横截面北侧附近的第二个SSC最大值是由于曲率导致的泥沙输送引起的泄漏。纵向流的科里奥利偏转也有助于将沉积物截留在北侧附近。这种机制在上河口很重要，在上河口，由于横向密度梯度而产生的水流较弱。

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