突扩、突跌掺气设施水力特性及影响因素的研究

发布时间：2018-03-01 11:12

本文关键词： 突扩突跌掺气浓度脉动压强模型试验掺气设施　出处：《昆明理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：我国蕴含非常丰富的水利资源,随着国家水电事业的快速发展,越来越多的高水头泄水建筑物的设计和建设,使得高速水力学问题越来越受到关注,高速水流的掺气减蚀问题变得愈加重要,掺气设施体形和来流水头等因素对高速水流水力特性的改变就变得十分重要。虽然很多人对掺气水流和脉动压力的研究取得了一定的成绩,但是在理论机理上的发展还是相对滞后,本文针对突扩、突跌体形的掺气设施进行模型试验,通过模型试验和理论分析的互相结合的方式,使用控制变量的研究方法,研究在不同流量、突扩宽度、跌坎高度下泄槽中水流掺气浓度分布以及变化规律、脉动总压强的分布情况、时均压强的变化、脉动压强的特点等掺气水流的水力特性。并且进行分析和讨论,得到以下成果:(1)通过控制变量法,改变流量、突扩宽度、跌坎高度三种影响因素,对泄槽中不同水深、不同轴线处的掺气浓度规律进行对比分析,得出经过突扩、突跌型掺气设施的水流,在泄槽中掺气浓度的变化规律,影响泄槽中不同位置掺气浓度的各种因素以及怎样才能获得良好的掺气效果。(2)介绍了脉动压强数据的分析和处理的方法,如何对脉动压强数据进行变异系数、偏态系数、峰度系数以及频谱特性的处理以及这些数据所反映的规律。(3)基于脉动压强数据处理上得出,泄槽中脉动总压强的变化规律,在冲击区脉动波动最大,沿程呈现出波动剧烈程度减弱,并在最后趋于稳定的规律。而泄槽中时均压强则是结合紊流特点呈现出先减小后增大的趋势。(4)通过控制变量法来研究不同流量下、不同掺气体形下泄槽中脉动压强的变化规律,通过对比分析泄槽中脉动压强的幅值、概率密度、频谱特性等特点,得出泄槽中水流脉动的变化规律。(5)分别对比不同掺气设施下水槽中脉动压强的幅值、频谱的特点,发现各种工况下掺气水流的脉动压强基本符合高速水流低频、高幅的特点。
[Abstract]:China is rich in water resources. With the rapid development of the national hydropower industry, more and more high-head drainage structures are designed and constructed, which makes the problem of high-speed hydraulics more and more concerned. The problem of air entrainment in high velocity flow becomes more and more important. The shape of aeration facilities and the first class factors of income have become very important to the change of hydraulic characteristics of high speed flow, although many people have made some achievements in the study of aeration flow and pulsating pressure. However, the development of theoretical mechanism is still lagging behind. In this paper, the model test is carried out for the aeration facilities with sudden expansion and sudden fall. Through the combination of model test and theoretical analysis, the research method of control variables is used. The distribution of aeration concentration, the distribution of total pulsating pressure, and the variation of average pressure in the channel with different flow rate, sudden expansion width and the height of falling ridge are studied. The characteristics of pulsating pressure and other hydraulic characteristics of aerated flow are analyzed and discussed, and the following results are obtained: 1) by controlling variable method, three factors affecting the flow rate, the width of sudden expansion, and the height of falling ridge are changed, and different water depths in the channel are obtained. The law of aeration concentration at different axes is compared and analyzed, and the variation law of aeration concentration in the vent is obtained through sudden expansion and sudden fall of air flow in aeration facilities. Various factors affecting aeration concentration at different locations and how to obtain good aeration effect are introduced in this paper. The methods of analyzing and processing pulsating pressure data, how to carry out variation coefficient and skewness coefficient of pulsating pressure data are introduced. The processing of kurtosis coefficient and spectrum characteristic and the law reflected by these data. Based on the data processing of pulsating pressure, it is concluded that the variation of total pulsating pressure in the vent is the most fluctuating in the impact zone. The fluctuation intensity decreases along the flow path and tends to be stable in the end, while the average pressure in the discharge tank shows a trend of first decreasing and then increasing according to the characteristics of turbulent flow) the control variable method is used to study the different flow rate. The variation law of pulsating pressure in different gas-doped discharge channels is analyzed by comparing the amplitude, probability density and spectrum characteristics of the pulsating pressure in the vent. The characteristics of amplitude and spectrum of pulsating pressure in flume under different aeration facilities are compared respectively. It is found that the fluctuating pressure of aerated flow basically accords with the characteristics of low frequency and high amplitude of high speed flow under various working conditions.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV135.2

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