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

实验性和分析作品到达了在IED水域表面上的风应力诱导的Andamine流动和水运输。水分竞争的驱动力在流体运动和风能上的重要作用。以下主题；（2）风应力产生的剪切层的剪切结构的实验和LES模拟速度和方向是在山脉包围的大坝顶部进行的，以研究其在储层周围的储层液体运动的地形。虽然风速与站点的数据相关。剪切。分析。在整个热级别上的夹带率和边界混合强度也取决于地表剪切应力，这将是水质预期工具的虚构步骤。风型界面界面是一种主要的机制，是分层水体中垂直水质交换的主要机制，以制定理论模型，在剪切量流动中的湍流（如风向驱动的流量）使用超声摄像机和PIV图像处理方法进行剪切层的测量。大阪和东京海湾的水力动力学，尤其是在东京湾，由于缺氧底部水的上升而出现了许多水质麻烦结构。 1996年5月，日本对水力工程的肯定。