异形构造水垫塘底板缝隙水流脉动压力传播特性研究

发布时间：2018-05-31 08:49

本文选题：水垫塘底板 + 异形构造　；参考：《天津大学》2014年硕士论文

【摘要】：我国水能可开发量和建设规模均居世界首位。这些工程在泄洪消能的过程中水头高,流量大,故高坝泄洪消能防护安全问题十分突出。为了达到消能和防冲的目的,通常使用混凝土保护高坝下游处的河床,并在高坝下游合适处构筑二道坝,形成消能防冲建筑物的一部分──水垫塘。由于高速水流及其产生的缝隙流的复杂性,高坝消力塘防护结构的安全一直是水利工程安全领域研究的热点问题。其中对防护结构体型进行优化,以达到增加抗失稳能力的目的,是提高泄流结构安全的方法之一。正是基于优化设计出发,相继提出了平底板,反拱形底板,透水底板和带键槽底板等型式。本文提出一种异形结构水垫塘底板,即底板带键槽加透水孔结构型式,以向家坝水垫塘模型试验为背景,基于模型试验结果,利用多种信号处理技术,研究了异形构造底板缝隙处水流脉动压力特性,研究的主要内容及研究成果为:(1)单板块情况下增设键槽对底板脉动压力传播特性的研究。结合向家坝水垫塘物理模型试验成果,分析了向家坝水垫塘底板增设键槽前后对底板上下表面以及垂直缝隙处脉动压力大小、分布规律,以及脉动压力的频域特性和相关特性。结果表明:带键槽底板可能产生的最大脉动上举力要比不带键槽小;增设键槽后下表面空间和时间积分尺度增大,增大了涡旋的持有性,加强了板块间的联系,从紊流角度分析出板块键槽的增设有利于结构的稳定性。(2)止水缝隙宽度对脉动压力传播的影响研究。在保证底板与基岩缝隙不变的情况下,改变板块间的止水缝隙,研究止水缝隙的改变对缝隙内水流脉动压力的影响。结果表明:随着止水缝隙的增大,产生的脉动上举力减小,有利于板块的稳定性;随着止水缝隙的减小,主频向低频移动,优势频带变窄,集中在0.1Hz以下。(3)底板缝隙宽度对脉动压力传播的影响。在保证底板与底板止水缝隙不变的情况下,改变底板与基岩缝隙,研究底板与基岩缝隙的改变对缝隙内水流脉动压力的影响。结果表明:随着缝隙厚度的增大,下表面测点均方差呈减小趋势;下表面测点的时间积分尺度也随之增大,涡旋的持有率增加。(4)异形构造底板稳定性研究。在板块上增设键槽并布置一定开孔率的透水孔,对比分析异形构造水垫塘底板与普通型式平底板水垫塘在高速水流的冲击作用下所受上举力特性等方面的异同点。结果表明:异形构造底板下表面脉动压强系数要小于一般构造底板下表面脉动压强系数。异形构造底板能有效地降低水流脉动能量,综合了透水底板与带键槽底板的优势,明显提高板块稳定性。
[Abstract]:The development capacity and construction scale of water energy in China are in the first place in the world. These projects have high water head and large discharge in the process of flood discharge and energy dissipation, so the safety problem of flood energy dissipation and protection of high dam is very prominent. In order to achieve the purpose of energy dissipation and erosion prevention, concrete is usually used to protect the riverbed downstream of the high dam, and to build two dams in the lower reaches of the high dam to form a part of the energy dissipation and scour prevention building, a part of the water cushion pond. Because of the complexity of high speed water flow and its crevice flow, the safety of the protective structure of high dam stilling pond has always been a hot topic in the field of water conservancy engineering safety. It is one of the methods to improve the safety of the leakage structure by optimizing the configuration of the protective structure to increase the ability of resisting instability. Based on the optimum design, the flat floor, the reverse arch floor, the permeable floor and the keyway floor are put forward one after another. In this paper, a kind of special shaped structure water cushion pond bottom plate with keyway and permeable hole structure is proposed. Based on the model test of Xiangjiaba water cushion pond, a variety of signal processing techniques are used. The characteristics of flow pulsation pressure at the crevice of irregular structural floor are studied. The main contents and results of the study are as follows: 1) in the case of single plate, the propagation characteristics of pulsating pressure on the bottom plate are studied by adding keyways. Combined with the physical model test results of Xiangjiaba water cushion pond, the fluctuating pressure magnitude, distribution law, frequency domain characteristic and correlation characteristic of fluctuating pressure on the upper and lower surface and vertical slot of Xiangjiaba water cushion pond floor before and after the addition of keyway are analyzed. The results show that the maximum pulsating lift force of the bottom plate with keyway is smaller than that without the keyway, and the space and time integral scale of the lower surface increases with the addition of the keyway, which increases the holding of vortex and strengthens the connection between plates. From the point of view of turbulence, the influence of the width of watertight gap on the propagation of fluctuating pressure is analyzed. The addition of plate keyway is beneficial to the stability of the structure. Under the condition that the gap between the bottom plate and the bedrock remains unchanged, the influence of the change of the gap on the pulsating pressure of the water flow in the gap is studied. The results show that the pulsating lifting force decreases with the increase of the sealing gap, which is beneficial to the stability of the plate, and with the decrease of the gap, the main frequency moves to the low frequency, and the dominant frequency band becomes narrower. The effect of gap width on pulsating pressure propagation is concentrated below 0.1Hz. Under the condition that the water stop gap between the bottom plate and the bottom plate is invariable, the influence of the change of the bottom plate and the bedrock gap on the flow pulsating pressure in the gap is studied. The results show that with the increase of gap thickness, the mean square deviation of measurement points on the lower surface tends to decrease, and the time integral scale of the measuring points on the lower surface also increases, and the holding ratio of vortex increases. 4) the stability of the irregular structural floor plate is studied. A keyway is added to the plate and a permeable hole with a certain opening rate is arranged. The similarities and differences between the bottom plate of a special shaped structure water cushion pond and the ordinary type of flat bottom water cushion pond under the impact of high speed water flow are compared and analyzed. The results show that the pulsating pressure coefficient is smaller than that of the general structural floor. The irregular structural floor can effectively reduce the flow pulsation energy, synthesizes the advantages of the permeable floor and the keyway floor, and obviously improves the stability of the plate.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV135.2

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