泄洪洞水击数值模拟研究

发布时间：2018-04-30 01:41

本文选题：特征线法 + 水击　；参考：《西北农林科技大学》2017年硕士论文

【摘要】：泄洪洞作为水利枢纽的主要泄水建筑物,保障枢纽安全运行。工作闸门位于泄洪洞末端,闸门的安全运行是泄洪洞发挥泄洪作用的必要条件,闸门运行过程中产生的水击可能引起闸门结构振动破坏。采用已发展成熟的特征线法进行泄洪洞水击的数值模拟,研究成果可为工作闸门的设计和闸门运行方案的制定提供参考。高水头、大流量泄洪洞的特点是水流流速高,应考虑流速对水击压强的影响。本文主要研究内容及研究结果:(1)当工作闸门匀速启闭时,尽管闸门启闭速度较小,但其运行过程中仍然伴随有水击现象的产生,水击压强周期性变化,往复作用于闸门上,可使闸门产生振动和噪音,甚至发生共振现象,导致闸门结构破坏。水击问题对泄洪洞的安全运行很重要,应当对其进行深入研究。(2)保持恒定流时工作闸门前水流压强不变且闸门启闭时间一定,数值模拟L=100m、L=300m、L=600m和L=900m四种洞长情况下的水击压强,分析对比计算结果可得出如下结论:工作闸门匀速启闭时,泄洪洞不同洞长情况下均有水击现象产生。泄洪洞洞长越大,水击压强振幅越大、振荡时间越长,水击作用于闸门上的瞬时荷载越大且作用时间越长,越容易引起闸门结构共振。在设计闸门结构和制定闸门启闭方案时,需考虑泄洪洞洞长对水击压强特性的影响,尤其当泄洪洞较长时,应尽量避免因水击作用时间过长、水击压强振幅过大而引起闸门结构破坏,影响泄洪洞以及整个水力枢纽的安全运行。(3)通过水工模型试验测出陕西省三河口水利枢纽泄洪底孔工作闸门上典型测点的脉动压力,再运用特征线法数值计算三河口泄洪底孔水击压强,最后将水击压强特性和脉动压强特性进行对比分析,结果表明:水击压强振荡频率大于脉动压强脉动频率,水击压强振幅大于脉动压强振幅,即水击压强振荡强度大于脉动压强脉动强度。当水击压强振荡频率和工作闸门自振频率接近时,由于水击压强作用于闸门上的瞬时荷载大于脉动压强作用于闸门上的瞬时荷载,所以水击压强比脉动压强更容易引起闸门结构振动。当设计三河口泄洪底孔工作闸门时,应当着重考虑水击压强对闸门结构的影响,而非脉动压强,并且闸门自振频率应当尽量避开水击压强振荡频率(5.39Hz),防止因闸门自振频率和水击压强振荡频率耦合而发生闸门结构共振破坏,为泄洪洞的安全泄洪提供保障。(4)在茨哈峡水电站泄洪洞工作闸门开启和关闭两种闸门运行工况下,对泄洪洞水击进行数值计算,并保持工作闸门启闭时间不变,改变闸门启闭方式,数值模拟泄洪洞工作闸门不同启闭方式下的水击压强,分析模拟结果可得:当工作闸门匀速开启时,水击发生于闸门开启初始阶段,水击压强振幅呈对数规律递减;当工作闸门匀速关闭时,水击发生于闸门关闭后阶段,水击压强振幅呈指数规律递减;工作闸门关闭工况下的水击压强振荡时间大于闸门开启工况下的水击压强振荡时间。在设计茨哈峡水电站泄洪洞工作闸门时,应避免因工作闸门自振频率和泄洪洞水击压强振荡频率(0.42Hz)耦合而引发闸门共振破坏。闸门运行方式对水击压强振荡频率没有影响,但对水击压强振幅影响较大。工作闸门加速开启、减速关闭的运行方式可有效降低水击对闸门结构的影响,甚至可忽略水击影响,排除了因水击压强振荡而引起闸门结构破坏的安全隐患,故推荐泄洪洞工作闸门采用加速开启、减速关闭的运行方式,例如当茨哈峡水电站泄洪洞工作闸门以0.000016m/s2的加速度开启、以-0.000016m/s2的加速度关闭时,水击对闸门结构的影响可显著减小。
[Abstract]:Hongdong, as the main discharge building of the hydro junction, ensures the safe operation of the hub. The working gate is located at the end of Hongdong. The safe operation of the gate is a necessary condition for discharging the flood discharge of Hongdong. The water shock produced during the operation of the gate may cause the vibration of the gate to be broken. The numerical simulation of the hole water hammer can provide reference for the design of the working gate and the formulation of the gate operation scheme. The high water head, the large flow discharge Hongdong is characterized by high flow velocity and the influence of the flow velocity on the water hammer pressure. The main contents and results are as follows: (1) the opening and closing speed of the sluice gate, in spite of the constant opening and closing of the gate, is the main research results. It is small, but it is still accompanied by water shock phenomenon in its operation, the periodic change of water hammer pressure and reciprocating on the gate can cause vibration and noise of the gate, even resonance phenomenon, resulting in the destruction of the gate structure. The water hammer problem is very important to the safe transportation of Hongdong. It should be studied in depth. (2) keep constant When the flow pressure is constant in front of the working gate and the opening and closing time of the gate is certain, the water hammer pressure is simulated under four holes of L=100m, L=300m, L=600m and L=900m. The result of analysis and comparison can draw the following conclusion: when the working gate is open and closed at a constant speed, there are water strikes in the case of different holes in Hongdong. The longer the cave length is, the greater the hole length of the flood discharge, the greater the hole length of the flood discharge. The greater the amplitude of the water hammer pressure, the longer the oscillation time, the greater the instantaneous load on the gate and the longer the action time, the more easy to cause the resonance of the gate structure. In designing the gate structure and making the gate opening and closing scheme, the influence of the length of the Hongdong hole to the pressure characteristics of the water hammer should be taken into consideration, especially when the Hongdong is long, we should try to avoid the cause. The time of water hammer is too long and the amplitude of water hammer pressure is too large, which causes the failure of the gate structure and affects the safe operation of the Hongdong and the whole hydraulic hub. (3) the hydrodynamic model test is used to measure the pulsating pressure of the typical point on the working gate of the bottom hole of the three estuary water conservancy project, and then the characteristic line method is used to calculate the flood discharge of the three estuarine estuary. The water hammer pressure characteristics are compared with the pressure intensity characteristics of the water hammer. The results show that the oscillation frequency of the water hammer pressure is greater than the pulsating pressure fluctuation frequency, and the amplitude of the water hammer pressure is greater than the fluctuating pressure amplitude, that is, the intensity of the water hammer pressure is greater than the pulse pressure intensity. When the vibration frequency is close, the instantaneous load on the gate is larger than the instantaneous load on the gate on the gate, so the water hammer pressure is more likely to cause the vibration of the gate structure than the pulsating pressure. The effect of the water hammer pressure on the gate structure should be seriously considered when designing the working gate of the three estuarine bottom hole. Pulsating pressure, and the gate self vibration frequency should avoid water hammer pressure oscillation frequency (5.39Hz) as far as possible to prevent the resonance damage of gate structure caused by the coupling of gate self vibration frequency and water hammer pressure oscillation frequency, and provide guarantee for safe discharge in Hongdong. (4) two gates are opened and closed at the sluice gate of Hongdong hydropower station. Under the operating condition, the water hammer in Hongdong is calculated, and the opening and closing time of the working gate is kept constant, the opening and closing mode of the gate is changed, and the water hammer pressure is simulated under the different open and close modes of the work gate of Hongdong. The analysis of the simulation results can be obtained: when the working gate is open at a constant speed, the water hammer occurs at the initial stage of the gate opening and the amplitude of the water hammer pressure. When the working gate closes at a constant speed, the water strike occurs after the gate closes, the amplitude of the water hammer pressure decreases exponentially, and the water hammer pressure oscillation time under the working gate closes is greater than the water hammer pressure oscillation time under the opening of the gate. The gate resonance destruction is caused by the free vibration frequency of the working gate and the coupling of the pressure oscillation frequency (0.42Hz) of the Hongdong water strike pressure. The operation mode of the gate has no effect on the frequency of the water hammer pressure oscillation, but it has great influence on the amplitude of the water hammer pressure. The working mode of the working gate is accelerated and the slow down and closing can effectively reduce the effect of the water hammer on the gate structure. Sound, even neglecting the impact of water hammer, excluding the safety hidden danger of the destruction of gate structure caused by the water hammer pressure oscillation, it is recommended that the Hongdong work gate adopt acceleration opening and slow down the operation mode, for example, when the sluice gate of the SSHA Gorge Hydropower Station opens the Hongdong gate with 0.000016m/s2 acceleration, it closes with the acceleration of -0.000016m/s2. The impact of water hammer on the structure of the gate can be reduced significantly.

【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV135.2

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