权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

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

分级材料的泥沙输送常常表现出非平衡行为，并随后伴随着河流分选过程。为了描述它所带来的现象，非平衡输运模型以每个颗粒尺寸的拾取率和步长为特征。当来自上游区域的沉积物输运受到抑制时，床面通过沉积物根据尺寸的选择性运动来调整其成分（尺寸分布）。特别是，供应的沉积物为零，床层变粗，并且其上的传输速率从上游端开始逐渐变为零（装甲层形成和传播）。同时，抑制的泥沙不为零，所有泥沙的粒度级仍被输送（输送速率最终等于供给的泥沙），但床面明显变粗（铺装）。这两种不同类型的床粗化过程可以用研究中提出的非平衡输运模型来描述。除了单调分选之外，还经常观察到交替分选：纵向交替分选和横向交替分选（纵向条纹分选）。这些分选不需要强制改变所提供的沉积物。各粒径的非平衡输送和床面成分的变化导致床面成分的不稳定。其形成过程可用本研究提出的非平衡输运模型来描述。在纵向交替分选的河流中，河床粗糙度的纵向变化严重改变了湍流结构，进而改变了其上悬浮泥沙的输运特征。基于湍流测量，推导了描述由于床层剪应力变化而引起的雷诺应力分布弛豫过程的模型，该模型是具有脉冲响应的卷积积分型模型。湍流动量交换与悬浮沉积物的湍流输送之间的相似性建议用雷诺应力分布的松弛模型来描述悬浮沉积物的非平衡浓度分布。较少的