Stratification effects by cohesive and noncohesive sediment
Stratification effects by cohesive and noncohesive sediment
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DOI：
10.1029/2000jc000435
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发表时间：
2001-10
影响因子：
--
通讯作者：
J. Winterwerp
中科院分区：
文献类型：
--
作者：
J. Winterwerp
本文研究河口海岸环境中细颗粒粘性和非粘性泥沙悬浮体与湍流相互作用引起的层化效应。一个简洁的文献综述表明，这种相互作用可能会导致明显的修改速度，垂直涡动粘度/扩散率，和雷诺应力的垂直配置文件。这种相互作用进一步研究了一维垂直（1DV）的数值模型，其中包括标准的k- 带浮力破坏项的湍流模型。科尔曼（1981）将该模型应用于实验结果表明，流速剖面的测量变化完全可以用沉积物引起的浮力效应来解释。有人认为，粘性沉积物的能力是..... ，cc，e、在粘性沉积物絮凝体沉积时形成流体泥浆层，这与非粘性沉积物的情况相反，在非粘性沉积物的情况下，沉积颗粒立即形成刚性床。因此，形成了双层流体系统，导致垂直混合过程的显著阻尼，进一步降低了承载能力。这种正反馈导致湍流场和浓度分布的灾难性崩溃。从经典的分层流理论推导出这种饱和行为的标度律。这一规律与1DV模式的一系列数值试验是一致的。它还预测了黄河中观测到的悬浮泥沙浓度，达到了正确的数量级。它的结论是，沉积物引起的浮力产生明显的分层效应，在已经中等悬浮泥沙浓度。在粘性泥沙的情况下，这些分层效应可能导致湍流场和悬沙浓度的垂直分布的灾难性崩溃。
This study focuses on stratification effects induced by the interaction between suspensions of fine-grained cohesive and noncohesive sediment and the turbulent flow in estuarine and coastal environments. A concise literature review reveals that this interaction may cause an appreciable modification of the vertical profiles of velocity, vertical eddy viscosity/diffusivity, and Reynolds stresses. This interaction is further studied with a one-dimensional vertical (1DV) numerical model, which includes the standard k- turbulence model with buoyancy destruction terms. Application of this model to the experimental results by Coleman (1981) shows that the measured changes in the velocity profile can be explained entirely by sediment-induced buoyancy effects. It is argued that capacity for cohesive sediment is ..... ,cc,e,, a fluid mud layer is formed upon the deposition of the cohesive sediment flocs, contrary to the case with noncohesive sediment, where the depositing grains immediately form a rigid bed. Thus a two-layer fluid system develops causing significant damping of the vertical mixing processes, decreasing the carrying capacity further. This positive feed back results in a catastrophic collapse of the turbulence field and the concentration profile. A scaling law for this saturation behavior is derived from classical stratified flow theory. This law is sustained with a series of numerical experiments with the 1DV model. It also predicts the suspended sediment concentrations observed in the Yellow River to the right order of magnitude. It is concluded that sediment-induced buoyancy yields appreciable stratification effects at already moderate suspended sediment concentrations. In the case of cohesive sediment these stratification effects can result in a catastrophic collapse of the turbulent flow field and the vertical profile of suspended sediment concentration.