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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

级配材料的泥沙输移往往表现出非平衡特性，并伴随着河流分选过程。为了描述这一现象，本文采用了以各粒径泥沙的起动率和步长为特征的非平衡输沙模型，当上游输沙受到抑制时，床面根据粒径大小选择性地输沙，从而调整其组成（粒径分布）。特别地，所供给的沉积物为零，床被粗化，并且在其上的输送速率从上游端逐渐变为零（装甲涂层形成和扩展）。当泥沙被抑制不为零时，泥沙仍被输移（输移率最终与供给率相等），但床面明显变粗（铺沙）。这两种不同类型的床层粗化过程可以用本文提出的非平衡输运模型来描述。 ...更多信息除了单一的排序外，还经常观察到交替排序：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。各粒径的非平衡输运和床面组成的变化导致床面组成的不稳定。本文提出的非平衡输运模型可以描述悬沙的形成过程，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湍流结构，从而改变了悬沙的输运特性。建立了一个描述床面切应力变化引起的沙应力分布松弛过程的卷积-积分型脉冲响应模型。紊动动量交换与悬移质紊动输移的相似性表明，悬移质浓度的非平衡分布可用应力分布的松弛模型来描述。少