自由跌水冲坑深度及水垫消能研究

发布时间：2018-05-07 17:21

本文选题：自由跌水 + 冲坑深度　；参考：《西华大学》2017年硕士论文

【摘要】：自由跌水的冲刷破坏问题一直是国内外学者研究的热点和难点。本文首先回顾了自由跌水和冲坑深度的理论研究、试验研究以及数值模拟的研究现状。再以某实际工程为背景,利用有机玻璃制作模型进行试验;接着,从自由跌水的特点出发,推导出了一个跌水冲坑深度的计算公式。将其结合已有的两个冲坑深度计算公式,对模型试验结果和实际工程进行了对比分析,验证了本文公式的正确性;最后,利用FLUNTE对实际工程的自由跌水进行了数值模拟。本文通过对以上内容的研究,得到了以下主要结论:(1)将前人从消能观点和水跃观点出发得到的冲坑深度与模型试验实测值进行比较。对比结果后发现,用消能观点冲坑深度公式得到的计算值与模型试验实测值相比偏大,而用水跃观点冲坑深度公式得到的计算值与模型试验实测值相比偏小。(2)本文从自由跌水的特点出发,在考虑水舌收缩的基础上,利用单个沙粒在稳定冲坑中的能量守恒建立平衡方程,推导得出了一个跌水冲坑深度的计算公式。由此公式得到的冲坑深度计算值与模型试验实测值的拟合曲线符合得很好。(3)利用消能观点、水跃观点、以及本文推导得到的冲坑公式对实际的自由跌水工程冲刷坑深度进行计算。结果表明,从消能观点公式得到的计算值和水跃观点公式得到的计算值较工程现场实测值都偏小,而从本文推导公式得到的计算值却与工程现场实测值非常接近。综合比较模型试验和实际工程,说明利用本文推导得到的冲坑公式,用来计算这类自由跌水形成的冲坑深度是相当准确的。(4)通过预设不同深度水垫塘的方法,对某个实际工程的自由跌水进行数值模拟,计算跌流的最大临底流速。计算结果表明:水垫塘的设置可以明显的减小水舌跌落后的最大临底流速;最大临底流速的大小会随水垫塘深度的增加而降低。在此基础上,结合消能效果和工程投资综合考虑,对该工程布置0.9m的水垫塘,既能满足较好的消能效果不产生冲坑,又能在经济上达到相对较优,由此可作为该工程减轻下游冲刷的整修方案。这种利用数值模拟计算最大临底流速来选定布置水垫塘的方法还可以应用到别的实际工程当中,为工程设计、整修提供参考,帮助解决这类自由跌水的冲刷问题。
[Abstract]:The problem of free water erosion has always been a hot and difficult problem for scholars at home and abroad. In this paper, the theoretical research, experimental study and numerical simulation of free water fall and scour depth are reviewed. Then taking a practical project as the background, the experiment is carried out by using a model made of plexiglass, and then a formula for calculating the depth of the sinkhole is derived from the characteristics of the free fall. Combined with the two existing formulas for calculating the depth of scour pit, the model test results are compared with the actual engineering results, and the correctness of the formula is verified. Finally, the numerical simulation of the free drop of water in practical engineering is carried out by using FLUNTE. In this paper, by studying the above contents, the following main conclusions are obtained: 1) the depth of the scour pit obtained from the viewpoint of energy dissipation and water jump is compared with the measured values of the model test. After comparing the results, it is found that the calculated values obtained by the formula of the depth of the scour pit from the viewpoint of energy dissipation are larger than the measured values of the model test. However, the calculated value obtained from the formula of the depth of the scour pit from the water jump viewpoint is smaller than the measured value of the model test. (2) based on the characteristics of free falling water and considering the shrinkage of the water tongue, Based on the energy conservation of a single sand particle in a stable scour pit, a formula for calculating the depth of the sinkhole is derived. The calculated value of scour depth obtained by this formula is in good agreement with the fitting curve of the measured value of model test.) using the viewpoint of energy dissipation, the viewpoint of water jump is used. And the formula of scour pit derived in this paper is used to calculate the depth of scour pit in free fall engineering. The results show that the calculated values obtained from the energy dissipation formula and the hydraulic jump viewpoint formula are smaller than those from the engineering site, but the calculated values obtained from the formula derived in this paper are very close to the engineering field measured values. By comprehensive comparison of model tests and practical engineering, it is shown that the formula of scour pit derived in this paper is quite accurate in calculating the depth of scour pit formed by this kind of free water drop. Numerical simulation is carried out on the free fall of a practical project, and the maximum critical bottom velocity of the falling flow is calculated. The results show that the setting of water cushion pond can obviously reduce the maximum near bottom velocity after the drop of the water tongue, and the magnitude of the maximum near bottom velocity will decrease with the increase of the depth of the water cushion pond. On this basis, considering the energy dissipation effect and the project investment synthetically, the water cushion pond with 0.9m arrangement can not only satisfy the better energy dissipation effect without producing scour pit, but also can achieve relatively better economy. This can be used as the project to reduce the downstream erosion of the refurbishment scheme. This method can also be applied to other practical projects, which can provide reference for engineering design and renovation, and help to solve the problem of this kind of free falling water scour.
【学位授予单位】：西华大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV653;TV135.2

【参考文献】