大型水库水温结构及取水口前流场研究

发布时间：2018-10-16 20:07

【摘要】：高坝大库的修建形成了大面积的停滞水域,加之太阳辐射等作用,水库内水体温度沿水深分层。下泄低温水将对农业灌溉和下游水生生态系统产生不利影响。为控制下泄水温,水电站分层取水的方式正逐渐被采用。理解和掌握水库水温分层结构的形成和变化规律,是研究取水口前流场和下泄水温的基础。取水口前流场又与下泄水温息息相关,系统研究温度分层水库取水口前流场,对指导分层取水取水口的设计及运行,以达到良好的控制下泄水温的效果是至关重要的。本文首先利用EFDC对某水库水温结构形成过程进行研究。然后,通过PIV流场测量试验系统,进行取水口前分层流动规律与流动机理的试验研究。最后,通过编写FLUENT边界条件,建立数学模型,进一步分析水温分布、取水口中心淹没深度和下泄流量对取水口前流场的影响。本文的主要研究内容及成果包括以下几个方面:(1)阐述了水库水温分层结构的形成机理、低温下泄水的危害、减免下泄低温水影响的相应措施以及常见的分层取水形式。对水库水温分层规律和下泄水温的研究方法进行归类总结。(2)利用ASTER GDEM数据获得某水库数字地形,以EFDC模型为基础,参考类似工程水温数学模型选定相关参数,建立该水库立面二维数学模型,对水库水温分层结构形成过程进行模拟。水库表层水体温度,不但呈现出季节性的变化规律,而且日间变化也十分明显;底层水体则比较稳定,仅仅随季节更替稍有变化。(3)按照光谱能量分布与太阳光谱能量分布保持一致原则,选择镝灯来模拟太阳辐射。通过镝灯对水面进行照射,对垂向水温结构进行测量,以观察人工辐射光源对水面下水体的加热效果,探索相关水面热交换下水温结构形成过程的试验方法。(4)将“水温试验相似理论”和PIV技术相结合,研制了专门的PIV流场测量试验系统,以三种典型水库水温分布为背景,改变取水口中心淹没深度进行不同组合,对取水口前流场进行试验研究,总结规律。(5)通过FLUENT的自定义函数功能,编写了库内水温分布和水密度随温度变化关系等边界条件,建立了适用于温度分层水库取水口前流场计算的数学模型,并得到试验数据的验证。针对在水温均一和三个典型月份水库水温分布,四个取水口中心淹没深度,三种下泄流量的工况进行了数值模拟。对水温分布、取水口中心淹没深度和下泄流量等因素对取水口前流场的影响进行了分析,总结了温度分层水库取水口前的流场规律。分析了取水口前流场与下泄水温的响应关系。
[Abstract]:The construction of large reservoir of high dam has formed a large area of stagnant water area, combined with the effect of solar radiation, the temperature of water body in the reservoir is stratified along the depth of water. Drainage of low-temperature water will adversely affect agricultural irrigation and downstream aquatic ecosystems. In order to control the temperature of drainage, the method of stratified water intake is gradually adopted in hydropower stations. Understanding and mastering the formation and variation of the stratified structure of reservoir water temperature is the basis of studying the flow field and the downwater temperature before the intake. The flow field is closely related to the outlet temperature. It is very important to study the flow field before the intake of the temperature stratified reservoir to guide the design and operation of the stratified intake so as to achieve a good effect of controlling the drainage temperature. In this paper, the formation process of water temperature structure of a reservoir is studied by EFDC. Then, the stratified flow law and flow mechanism before intake are studied by PIV flow field measurement system. Finally, by compiling FLUENT boundary conditions, a mathematical model is established to further analyze the influence of water temperature distribution, the depth of water intake center submergence and the lower discharge on the flow field before the intake. The main contents and achievements of this paper include the following aspects: (1) the formation mechanism of reservoir water temperature stratification structure, the harm of low-temperature water discharge, the corresponding measures to reduce the influence of low-temperature drain water and the common layering water intake form are expounded. The research methods of reservoir water temperature stratification and drainage water temperature are classified and summarized. (2) the digital topography of a reservoir is obtained by using ASTER GDEM data. Based on the EFDC model, the relevant parameters are selected with reference to the similar engineering water temperature mathematical model. A two-dimensional mathematical model of the vertical plane of the reservoir is established to simulate the formation process of the water temperature stratification structure of the reservoir. The surface water temperature of the reservoir not only shows seasonal variation law, but also the daytime variation is very obvious, while the bottom water body is relatively stable. (3) according to the principle that spectral energy distribution is consistent with solar spectral energy distribution, dysprosium lamp is selected to simulate solar radiation. The water surface was irradiated by dysprosium lamp and the vertical water temperature structure was measured in order to observe the heating effect of artificial radiation light source on the water body under the water surface. The experimental method of formation process of water temperature structure under relevant water surface heat exchange is explored. (4) combining the similarity theory of water temperature test with PIV technology, a special PIV flow field measuring and testing system is developed, which is based on the water temperature distribution of three typical reservoirs. Different combinations of the submerged depth of the intake center are carried out, the flow field before the intake is studied experimentally, and the rules are summarized. (5) through the function of self-defined function of FLUENT, the boundary conditions such as the distribution of water temperature and the variation of water density with temperature in the reservoir are compiled. A mathematical model for the calculation of the flow field before the intake of a temperature stratified reservoir is established, and the experimental data are verified. Numerical simulation was carried out for the reservoir water temperature distribution in three typical months, the submergence depth of four intake centers, and the three down-discharge conditions in the case of uniform water temperature and three typical months. The effects of water temperature distribution, intake center submergence depth and discharge rate on the flow field before the intake are analyzed, and the flow field law before the intake of the temperature stratified reservoir is summarized. The response relationship between the flow field and the temperature of the outlet is analyzed.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TV697.21

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