桥位区河道切滩过流特性试验及数值模拟研究

发布时间：2018-03-06 23:10

本文选题：跨河桥梁　切入点：断面补偿　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：跨河桥梁工程,大多占用河道过流断面,墩台改变原有河道水流结构,将对桥梁、堤防稳定及河道过流产生不利影响。工程实际中一般通过切滩、疏浚进行河道断面补偿,合理确定断面补偿方案需考虑因素众多,目前研究成果较少,工程实践中主要以经验为主,开展河道切滩过流特性试验及数值模拟研究很有意义。论文通过物理模型试验和数值模拟,就影响河道过流能力的补偿面积、切滩坡比、疏浚深度、疏浚边界坡比等主要因素进行了研究。对概化的复式顺直型河道进行了物理模型试验,分析了不同工况的墩周河道水流特性,探讨了河道断面补偿部分过流能力与诸多因素之间的关系;采用Fluent软件建立了单墩阻水的三维数值模型,基于标准的k-?两方程湍流模型,采用有限体积法对流体运动的控制方程进行离散、VOF方法进行自由面追踪、壁面函数法求解壁面区流动,分析了不同工况下的河道水流特性及断面补偿部分过流能力,并与试验结果进行了对比,得到如下主要结论:(1)对桥墩周边水流结构试验表明,桥墩周边水流的紊动具有各向异性的特点,L4测线处,横向紊动强度*u、纵向紊动强度*v自水面向下随着水深的增加,呈现逐渐增大的趋势,在近壁面附近达到最大值,然后又逐渐减小。不同方向上的雷诺切应力沿垂向分布差别较大,其分布形态与正弦曲线相似,但变化幅度具有一定的差异。(2)对桥墩上游最大壅水高度进行分析表明,采取断面补偿措施可有效降低上游最大壅水高度,壅水高度降低程度与断面补偿面积呈正相关。断面补偿作用对桥墩处流场的影响比较明显,进行断面补偿后,河床面上桥墩附近水流的纵向流速xV、横向流速yV、及动水压力均有不同程度的降低。(3)无论采取何种断面补偿型式,断面补偿部分通过的流量Q与断面补偿面积呈正相关,即随着断面补偿面积的增大而增大。采取切滩补偿方式时,切滩坡比对过流能力的影响却并不显著。采用疏浚方式进行断面补偿时,边坡系数为3时断面补偿部分通过的流量最大,过流能力随疏浚宽深比的增大,呈先减小后增大的趋势。
[Abstract]:Most bridge projects across the river take up the section of river flow, and the piers and abutments change the flow structure of the original channel, which will have a negative impact on the bridge, the stability of the levee and the flow of the river. In practice, the channel section compensation is usually carried out by dredging and cutting the beach. There are many factors to be taken into account in determining the section compensation scheme reasonably. At present, there are few research results, and experience is the main factor in engineering practice. It is of great significance to study the characteristics and numerical simulation of river channel cut beach flow. Through the physical model test and numerical simulation, the compensation area, slope ratio and dredging depth of river channel are studied. The main factors, such as the slope ratio of dredged boundary, are studied. The physical model tests are carried out to analyze the flow characteristics of the channel around the pier under different working conditions. This paper discusses the relationship between the overflow capacity of the section compensation and many factors, and establishes a three-dimensional numerical model of blocking water of a single pier by using Fluent software, based on the standard k-? In the two-equation turbulence model, the finite volume method is used to discretize the governing equations of fluid motion for the free surface tracing, and the wall function method is used to solve the flow in the wall area. In this paper, the characteristics of river flow and the capacity of section compensation are analyzed under different working conditions, and the results are compared with the experimental results. The main conclusions are as follows: 1) the experimental results on the flow structure around the bridge piers show that, The turbulence around the pier is anisotropic. The transverse turbulence intensity is u, and the longitudinal turbulence intensity increases gradually with the increase of water depth from the surface of the water, and reaches the maximum near the wall. Then decrease gradually. The distribution of Reynolds shear stress along vertical direction is quite different, and its distribution pattern is similar to sine curve, but the range of variation is different to a certain extent. The analysis of maximum backwater height in upstream of bridge pier shows that the distribution of Reynolds shear stress in different directions is similar to that of sinusoidal curve. Adopting cross-section compensation measures can effectively reduce the maximum backwater height upstream, and the degree of backwater height reduction is positively related to the cross-section compensation area. The effect of cross-section compensation on the flow field at the pier is obvious, and after the cross-section compensation, the effect of cross-section compensation on the flow field at the bridge pier is obvious. The longitudinal velocity (x V), transverse velocity (y V) and dynamic pressure of the flow near the pier on the river bed are all reduced to varying degrees. (3) no matter what type of cross-section compensation is adopted, the flow rate Q passing through the section compensation section is positively correlated with the compensation area of the section. That is to say, with the increase of cross-section compensation area, the effect of slope ratio on cross-flow capacity is not significant when the compensation method is adopted, and the dredging method is used to compensate the cross-section. The coefficient of slope is the largest in the compensation part of 3:00 section, and the overflow capacity decreases first and then increases with the increase of the ratio of dredging width to depth.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U442.3

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