浅水风生波、流特性的实验研究

发布时间：2018-03-20 04:24

本文选题：浅水　切入点：风生波　出处：《上海交通大学》2014年硕士论文　论文类型：学位论文

【摘要】：湖泊中风生波是水表面受到风的摩擦剪应力和波浪背面受到风压力作用引起的。其水面受到风应力的扰动，激发风浪使其成长为风生波。且在粘滞力作用下表层水体带动下层水体沿风向运动，湖泊中水体因此而产生壅高。由于湖泊水体质量守恒，近湖底水体产生与风向相反的补偿流，从而在湖泊中产生纵向的风生环流。我国众多湖泊均为浅水型湖泊，湖泊水体在风生波作用下的运动复杂且剧烈，湖底淤泥和污染物等易受浅水风生表面波的扰动而产生悬浮，而起扬的底泥与污染物等在风生流的作用下将产生输移。因此浅水风生波、风生流是浅水湖泊中底泥等物质再悬浮和输移的直接动力来源，，是研究浅水湖泊水动力学的关键。南京水利科学研究院建设水平比尺为1：500的太湖三维物理模型，对湖区水动力变化规律、湖区污染物运输规律和入湖河流与湖泊水流联动机理进行研究。本文采用物理模型实验的方法对浅水湖泊的风生波、流进行了实验研究。具体研究内容如下： 1)在上海交通大学的风浪流水槽中采用可升降假底装置模拟了典型浅水湖泊的浅水效应，研究了不同浅水条件下风生波的频谱、波高、波长以及壅水等特性，并将实验得到的波长、波高及壅水结果与已有经验公式计算结果进行了对比分析。结果表明，本实验条件下风生波有明显的浅水效应，且在浅水条件下存在一个临界风速，浅水风生波的波高、波谱变化规律与该临界风速有关。 2)在浅水风生流实验中，首先利用示踪粒子测量不同水深和不同特征风速条件下表面流速的大小，实验结果表明随着风速的增大表面流速呈线性增长趋势，且随着水深的增大表面流速减小。随后采用粒子成像测速仪(PIV)和声学多普勒流速仪(ADV)设备对给定测量段断面处的垂向平均流速分布进行测量。测量结果表明，两种测量手段所得的风生流场吻合较好，而且测量结果与理论解析解一致，即水槽模型能用来模拟研究浅水风生流的流场特性。 3)在加糙技术模拟浅水风生波的实验中，通过表面加糙和底面加糙的方式进行实验研究。表面加糙方式为：由水面拍击方法模拟风生表面波，增加水表面粗糙度；由风机吸风模拟风场作用产生风壅水，以此探索一种将水面拍击与风机技术结合的浅水风生波模拟技术，以期在满足模型壅水率的前提下，降低风机能耗。底面加糙方式为：在模型底面铺设加糙设备，增大底面粗糙度，以此提高壅水率，以期在满足模型壅水率的前提下，降低风机能耗。 4)根据本文实验中测得的不同实验水深、不同特征风速条件下的壅水率，给出了满足太湖模型壅水要求条件下，特征风速与水深的关系曲线。由该关系曲线可知：当水深给定时，壅水率随风速的增大而呈增大趋势；当风速给定时，壅水率随水深的增大而减小。同时根据风生波波高实验结果，给出了不同壅水率条件下，太湖模型最大风吹程的平均波高随水深的关系曲线。这两条关系曲线对预报太湖模型的壅水高度和平均波高有重要的实用价值。
[Abstract]:The lake wind-driven wave is the water surface by the wind friction shear stress and wave back is caused by wind pressure. The surface disturbance of wind stress, stimulate the waves to grow as wind-driven waves. And the viscous force under the action of surface water to the bottom water along the wind direction movement, resulting in lake water high. Because the lake water quality conservation, water flow near the bottom and the opposite direction of compensation, resulting in vertical wind-driven circulation in the lakes. Lakes in China are shallow lake, lake water in the role of wind wave motion under the complex and intense, and vulnerable to pollutants such as silt disturbance waves in shallow water. Due to suspension, and Yang sediment and pollutant transport in the wind-driven flow will produce under the action of wind wave in shallow water. Therefore, wind-driven current is directly from the shallow lake material resuspension and transport The source of power is the key of shallow lake water dynamics. Nanjing Scientific Research Institute of water conservancy construction level of Taihu three-dimensional physical model of 1:500 scale, the variation of hydrodynamic and pollutant transport of Lake Lake, the river into the lake and lake water linkage mechanism was studied.
This method and physical model test of wind wave in shallow lakes, streams were studied. The main research contents are as follows:
1) by lifting the false bottom device simulation the shallow water effect typical shallow lake in the storm water tank of Shanghai Jiao Tong University, studied the wave height spectrum, different wind wave in shallow water, the wavelength and the backwater and other characteristics, and the wavelength, wave height and water level results and the experience formula calculation results are compared the analysis results showed that the experimental conditions of wind wave in shallow water has obvious effect, and there is a critical wind speed in shallow water conditions, shallow water wind wave height variation, spectrum associated with the critical wind speed.
2) in shallow water current flow in the experiment, first using the tracer particle measurement of surface flow velocity under different water depth and wind speed characteristics of the size, the experimental results show that with the increase of wind speed of surface flow velocity increases linearly, and with the surface velocity decreased with increasing depth. Then using particle image velocimetry (PIV) and acoustic Doppler velocimeter (ADV) the equipment section given measuring section were measured to the average vertical velocity distribution. The measurement results show that the two kinds of wind-driven current measurement method and the measurement result agree well with analytical solution, which can be used to simulate the flow field model of shallow water current flow.
3) roughening technology in simulation of shallow water wave by wind experiment, through the experimental research of surface roughness and surface roughness. The surface roughness is: the surface slap method to simulate the wind-driven surface wave, increase the surface roughness by the suction fan; simulation of wind field generated wind backwater, so to explore a combination of water and slap fan technology simulation technology of shallow water wave by wind, in order to meet the model backwater rate, reduce the energy consumption of the fan. The bottom surface roughness is laying face roughness in model of bottom equipment, increase the bottom surface roughness, so as to improve the rate of water. In order to meet the model backwater rate, reduce the energy consumption of the fan.
4) according to the different experimental depth measured in this experiment, the different characteristics of wind speed under the condition of backwater rate is given to meet the Taihu model water requirement, curve characteristics of wind speed and depth. The curves show that when the water depth is given increasing backwater rate with wind speed increases; when the wind speed is given, the backwater rate with depth increasing. At the same time according to the wind wave experimental results, given the conditions of different water ratio, the average wave height of Taihu model with maximum wind blowing distance curve of water depth. The two curves of forecast model of Taihu in the backwater height and average wave height it has important practical value.

【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV139.2

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