【作者】 刘昉；

【导师】 练继建；

【作者基本信息】 天津大学 ， 水利水电工程， 2007， 博士

【摘要】 近年来,随着高坝的不断兴建,泄洪消能防护结构因为水流脉动荷载的强烈作用而发生破坏的问题受到了极大的关注。目前在建和拟建的大坝,无一例外要对泄洪消能防护结构的稳定性问题进行系统的研究。虽然对水流脉动荷载的研究已经取得了一定成果,但是由于在理论上缺乏足够的认识,许多决定结构安全性的关键数据仍然要通过相应的水工模型试验来获得。因此如何利用模型试验结果来正确估计原型上的脉动荷载就成为工程上所关心的内容。对于脉动壁压在缝隙内的传播规律,理论计算还只限于简单边界条件下的问题,而系统的试验研究成果也比较少。本文将对这些问题进行深入的研究,具体内容包括:(1)综合流场影响理论和涡旋传递理论对脉动壁压的成因与机理进行了探讨,从N-S方程出发讨论了脉动壁压的相似性问题。(2)对脉动壁压相似律试验结果的幅值特征进行了分析,内容包括脉动壁压强度、偏差系数、峰度系数、概率密度函数和特征函数等,并在分析结果的基础上综合研究了系列比尺模型脉动壁压幅值特征的相似律问题。(3)对脉动壁压相似律试验结果的相关特征及频谱特征进行了分析,内容包括自相关函数、时间积分尺度、瞬时空间相关函数、空间积分尺度和功率谱密度函数等,并在分析结果的基础上综合研究了系列比尺模型脉动壁压相关特征和频谱特征的相似律问题。(4)对脉动壁压在缝隙内传播规律试验结果进行了分析,内容包括缝隙内脉动压强沿程分布和缝隙宽度的影响,衬砌底板块上下表面点脉动压强特征、上下表面脉动荷载特征、脉动上举力特征和脉动壁压点面转换关系等。(5)通过大涡模拟对脉动壁压进行了数值计算,并将计算结果与试验结果进行了对比。综合以上研究发现,水跃区和冲击射流区内脉动壁压符合重力相似律。脉动壁压在缝隙内以压力波的形式传播,沿程分布规律与衬砌底板块上表面脉动壁压的分布规律一致,强度则随缝隙宽度的增大而减小。更多还原

【Abstract】 In recent years, as a continual construction of high dams, it is paid more attention to that the protective structures of energy dissipators failed during the flood discharge. Associated with this process are severe pressure fluctuations which must be a matter of concern in the structural design of the protective structures of energy dissipators. The study on the pressure fluctuations had achieved great success in the past years, but because of the lack of sufficient theoretics, hydraulic model experiments however play an important role in the design of the protective structures. A similarity law of the pressure fluctuations is a key criterion that ensures the safety of the results measured from the model being transformed to the prototype. As to the characteristics of the propagation of the pressure wave within the contraction joints, theoretical calculation can only solve the simple boundary condition problems, and the experiment results are not enough at present. To resolve the above problems, this paper will discuss the following things:(1) Based on Navier-Stokes equation and theory of vorticity transport, the genesis and mechanism of the pressure fluctuations is discussed, and its similarity law is derived.(2) It is analyzed in the paper of the characteristics of the amplitude value of the pressure recorded in the experiments. It consists of the computation of average, standard deviation, skewness, kurtosis, probability density function and characteristic function of the pressure data, etc. From the results, a similarity law of the amplitude value of the pressure is discussed.(3) It is analyzed in the paper of the characteristics of the correlation and spectrum of the pressure recorded in the experiments. It consists of the computation of autocorrelation, integral time-scale, spatial correlation, integral length-scale, and power spectral density function of the pressure data, etc. From the results, a similarity law of the correlation and spectrum of the pressure is discussed.(4) It is analyzed in the paper of the characteristics of the propagation of the pressure wave within the contraction joints recorded in the experiments. It consists of the spatial distribution of the point pressure fluctuations within the joints and the influence of joints width, point pressure fluctuations on the slabs upper faces and lower faces, hydrodynamic loads, uplift loads, transform between point pressures and forces, etc.(5) Finally, a numerical calculation using large eddy simulation equation is carried out to computing the pressure fluctuations in the hydraulic jump, and its computing results is compared with the results from the experiments.From the above study, it can be drawn that in the hydraulic jumps and plunge pools, the similarity law of the pressure fluctuations obeys the Froude law. The propagation form of the pressure fluctuations in the joints is pressure wave. It has the similar spatial distribution of the pressure fluctuations between the upper faces and lower faces of the slabs. The attenuation of the pressure amplitude increases directly with the joint width.更多还原