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Mechanics of Sediment Transport of Graded Materials and Fluvial Sorting

分级材料输沙机理及河流分选

基本信息

批准号：
01550401
负责人：
TSUJIMOTO Tetsuro
金额：
$ 1.41万
依托单位：
Kanazawa University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1990
项目状态：
已结题

项目摘要

Sediment transport of graded materials often shows non-equilibrium behavior and subsequently it accompanies fluvial sorting process. In order to describe the phenomena it brings about, non-equilibrium transport model characterized by pick-up rate and step length for each grain size.When the sediment transport supplied from the upstream region is suppressed, the bed-surface adjusts its composition (size distribution) by selective movement of sediment according to the size. Particularly, the supplied sediment is zero, the bed is coarsened and the transport rate over it becomes zero increasingly from the upstream end (armor coat formation and propagation). While, the suppressed sediment is not zero, all size-fraction of sediment are still transported (the transport rate becomes equal to the supplied one finally) but the bed surface is obviously coarsened (pavement). These two different types of bed coarsening process could be described by the non-equilibrium transport model proposed in th … More is study.Besides monotonous sorting, alternate sortings are often observed : longitudinally alternate sorting and laterally alternate sorting (longitudinal stripes of sorting). These sortings do not require the forced change of supplied sediment. Non-equilibrium transport for each grain size and the change of bed-surface composition brings about an instability of the bed-surface composition. The formation processes could be described by the non-equilibrium transport model proposed in this study.In a stream with longitudinally alternate sorting, the longitudinal change of bed roughness severely changes the turbulent structure and subsequently the characteristics of suspended sediment transport over it. Based on the turbulence measurements, a model to describe the relaxation process of Reynolds-stress distribution due to the change of the bed shear stress was derived, which was a convolution-integral type with an impulse response. The similarity between the turbulent momentum exchange and the turbulent transport of suspended sediment suggested a description of non-equilibrium concentration distribution of suspended sediment with the relaxation model prepared for the Reynolds-stress distribution. Less

级配材料的泥沙输运往往表现出非平衡行为，并伴随着河流分选过程。为了描述泥沙运动所带来的现象，提出了一种非平衡泥沙输运模型，该模型以泥沙上升率和泥沙步长为特征，在上游泥沙输移受到抑制的情况下，床面根据泥沙的大小对泥沙的组成(粒度分布)进行选择性的调整。特别是，提供的泥沙为零，河床变粗，从上游端(装甲形成和传播)开始，床面上的输送速率逐渐变为零。当被抑制的泥沙不为零时，所有粒级的泥沙仍然被输送(最终输沙率与供沙率相等)，但床面明显变粗(路面)。这两种不同类型的床层粗化过程可以用…提出的非平衡输运模型来描述更多的是研究。除了单调的排序，经常可以观察到交替排序：纵向交替排序和横向交替排序(排序的纵向条纹)。这些分选不需要强制改变所提供的沉积物。各种粒度的非平衡输运和床面组成的变化导致床面组成的不稳定。在纵向交替分选的河流中，床面粗糙度的纵向变化严重地改变了水流的紊动结构，进而改变了悬沙的输移特性。在湍流测量的基础上，建立了一个描述床面剪应力变化引起的雷诺应力分布松弛过程的模型，该模型是一个具有脉冲响应的卷积积分型模型。悬移质的动量交换和湍流输运的相似性表明，悬沙的非平衡浓度分布可以用雷诺应力分布的松弛模型来描述。较少