Experimental and Analytical Study on Water Quality Transfer Induced by Wind Shear Stress in Stratified Water Areas

分层水域风切应力引起水质转移的实验与分析研究

基本信息

批准号：
06650566
负责人：
MICHIOKU Kohji
金额：
$ 1.15万
依托单位：
Kobe 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：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650566/
关键词：
Density Currents Wind Stress Upwelling Vertical Mixing Lake Dynamics Water Front Hydro Environment Bay Area Wind Stress Lake Dynamics

项目摘要

Experimental and analytical works are carried out to examine flow and water quality transport induced by wind shear stress acting on the surface of stratified water areas. Such a situation is found in many enclosed water areas such as lakes, reservoirs, land-locked bays, where density stratification plays an important roles in fluid motions and the wind shear stress is a major driving force of water mass transport. From a view point of hydrosphere environment it is urged to construct an environmental assessment tool based on a theoretical background of hydrodynamics. In order to meet engineering demands, this research project is organized so as to cover the following three themes ; (1) field and numerical works on wind field properties and formation mechanism of wind-driven circulation, (2) experimental and LES simulation on turbulent structure of shear layr generated by wind stress, (3) three dimensional modeling of flow field in bay areas. The major results are followed.(1) A filed m … More easurement on wind velocity and direction is carried out at the top of a dam surrounded by mountains to investigate its properties as a driving force of reservoir fluid motions. It is found the wind direction is profoundly affected by the local terrain around the reservoir and is almost independent on the wind direction observed at a meteorological station located in a nearby flat area, while the wind speed there has a good correlation with data from the station. From this, it is suggested one need to carefully examine wind fields before theoretically reproducing wind-driven fluid motions in water areas by using wind data. A k-epsilon turbulence modeling is performed to examine the vertical circulation and mixing driven by the wind shear. Through the analysis, it is found how amount of bottom water upwelling, entrainment rate across the thermocline and the boundary mixing intensity depend on the density structure as well on the surface shear stress, which would be a first step of construction of water quality prediction tools.(2) It is known that the wind-driven shear layr developing at the thermocline interface is a major mechanism being responsible for vertical water quality exchange in a stratified water body. For formulating a theoretical model being able to describe turbulence in a shear-dominant flow like wind-driven flows, it is required to find its dynamics. A velocity measurement of shear layr is carried out by using a ultrasonic video camera and PIV image processing method. Some hierarchy of organized turbulent structures are found there, which are quite similar to those observed in wall turbulence. LES performance in reproducing flow structure is quite well ; the result are in almost complete agreement with the experiment. It is investigated how the shear-layr turbulence promotes water quality transfer in wind-driven flow fields.(3) Experimental and numerical investigation are carried out to get hydrodynamics in Osaka and Tokyo Bays. Especially in Tokyo Bay, many water quality troubles arise due to upwelling of anoxic bottom water, which brings serious damages to fishery farms along the coast. A laboratory experiment is carried out to examine mechanism of bottom water upwelling. A functional relationship of the upwelling rate on wind velocity and density structure. A three dimensional model is also parameterized in order to reproduce wind-driven currents in the two bays. Model performance is quite satisfactory ; the simulated flow fields are in good agreement with the field data. It is expected that the model could be of practical use in assessing environmental changes after some construction works in bays and coastal areas.The final report is published and delivered to Japanese institutions of hydraulic engineering in May 1996. Less

进行实验和分析工作，以检查作用在分层水域表面的风剪应力引起的流动和水质运输。在许多封闭的水域（例如湖泊，水库，陆上锁定的海湾）中发现了这种情况，其中密度分层在流体运动中起着重要作用，风剪应力是水质量运输的主要驱动力。从水圈环境的角度来看，敦促基于水动力学的理论背景来构建环境评估工具。为了满足工程要求，该研究项目的组织以涵盖以下三个主题；（1）风场特性以及风驱动循环的形成机理的田间和数值作品，（2）风应力产生的剪切层的湍流结构的实验和LES模拟，（3）海湾区域中流场的三维模型。遵循主要的结果。（1）提交的M…在风速和方向上进行了更多的地役权，在被山脉包围的大坝顶部进行，以研究其作为储层流体运动的驱动力。发现风向受到储层周围的当地地形的深刻影响，几乎独立于在位于近乎平坦区域的气象站观察到的风向，而那里的风速与站点的数据有良好的相关性。由此，建议人们需要仔细检查风场，然后使用风数据在神秘地重现水域中的风流流体运动。进行了K- Epsilon湍流建模，以检查垂直循环和通过风剪切的混合驱动。通过分析，发现如何在表面剪切应力上取决于密度结构，这将是水质预测工具的构建的第一步。为了制定理论模型能够描述剪切优势流中的湍流，如风向流，需要找到其动力学。使用超声摄像机和PIV图像处理方法进行剪切层的速度测量。在那里发现了有组织的湍流结构的一些层次结构，这与壁湍流中观察到的层次结构非常相似。 LES在再现流结构中的性能非常好。结果与实验几乎完全一致。研究了剪切 - layr湍流如何促进风向流场中的水质转移。（3）实验和数值投资以在大阪和东京海湾获得流体动力学。尤其是在东京湾，由于缺氧底部水的上升造成的许多水质麻烦，这给沿海地区带来了严重的损害。进行了实验室实验，以检查底水上升的机理。上升速率在风速和密度结构上的功能关系。还对三维模型进行了参数化，以便重现风力驱动的模型性能非常满意。模拟流场与字段数据非常吻合。预计该模型在评估海湾和沿海地区的一些建筑作品后可以在评估环境变化方面具有实际使用。最终报告是在1996年5月发布并交付给日本水解工程机构的。