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Reinvestigation of Sediment Transport Mechanism due to Wave Action from the Viewpoint of Fluid Mechanics

从流体力学角度重新研究波浪作用泥沙输送机制

基本信息

批准号：
01460180
负责人：
HORIKAWA Kiyoshi
金额：
$ 3.07万
依托单位：
Saitama University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1989
资助国家：
日本
起止时间：
1989 至 1991
项目状态：
已结题

项目摘要

The aim of the present research project is (1) to review carefully a great number of research papprs presented so far in relation to sediment transport mechanism due to wave action, and (2) to carry out a series of laboratory investigation on oscillatory boundary flow over ripple models. The basic concept of this research project is reexamine the mechanism of sediment motion induced by time-dependent fluid motion through the view of fluid dynamics. In order to clarify the interaction of the fluid motion and the sediment particle motion, two types of fixed ripple models are installed separately inside an oscilla. tory flume, the size of which are nearly similar to sand ripples generated along the sea bottom by wave action. The first type has a sharpe crested form and the second a round crested form. The former has a some what different shape from the natural sand ripple, but has an advantage to simplify the flow pattern. A 2-D laser Doppler velocimeter (LDV) is effectively used to measure the flow characteristics of mean velocity, fluctuation of velocity components, turbulence intensity, Reynolds stress, and. kinematic eddy viscosity. These terms are diagrammatically shown on a raph for each phase of oscillation, through which formation and disappearance vortices can be visualized. By bomparing these data for sharpe and round crested models, it is clearly shown that the intensity of vortex formed behind a sharp crest is much stronger than that of vortex behind a round crest. In order to look at the temporal and spatial variation of vortex distribution with phase, the measured velocity records are used to calculate the vorticity at each grid point. By using the above data, the development and dissipation process of overall vortex intensity are quantitatively studied.

本研究项目的目的是（1）仔细回顾迄今为止提出的大量与波浪作用引起的泥沙输运机制相关的研究成果，（2）对涟漪模型上的振荡边界流进行一系列实验室研究。本课题的基本思路是从流体动力学的角度重新审视流体时变运动诱发泥沙运动的机理。为了研究水流运动与泥沙运动的相互作用，在水槽中分别安装了两种固定式涟漪模型。tory水槽，其大小几乎类似于波浪作用下沿沿着产生的沙波纹。第一种类型有一个尖锐的冠状形式和第二个圆冠状形式。前者与天然沙涟漪的形状有一定的差异，但具有简化流型的优点。利用二维激光多普勒测速仪（LDV）测量了湍流的平均速度、速度分量脉动、湍流强度、雷诺应力和雷诺数等流动特性。运动涡动粘度这些项在图上以图解方式表示出振荡的每一相，通过这些项可以看到涡旋的形成和消失。通过对尖峰和圆峰模式的比较，可以清楚地看出尖峰后形成的旋涡强度比圆峰后的旋涡强度大得多。为了考察涡量分布随相位的时空变化，利用实测速度记录计算了各网格点的涡量。利用这些资料，定量地研究了总涡强度的发展和消散过程。