本文選題：跨河橋梁　切入點：斷面補償　出處：《合肥工業(yè)大學》2017年碩士論文　論文類型：學位論文

【摘要】：跨河橋梁工程,大多占用河道過流斷面,墩臺改變原有河道水流結(jié)構(gòu),將對橋梁、堤防穩(wěn)定及河道過流產(chǎn)生不利影響。工程實際中一般通過切灘、疏浚進行河道斷面補償,合理確定斷面補償方案需考慮因素眾多,目前研究成果較少,工程實踐中主要以經(jīng)驗為主,開展河道切灘過流特性試驗及數(shù)值模擬研究很有意義。論文通過物理模型試驗和數(shù)值模擬,就影響河道過流能力的補償面積、切灘坡比、疏浚深度、疏浚邊界坡比等主要因素進行了研究。對概化的復式順直型河道進行了物理模型試驗,分析了不同工況的墩周河道水流特性,探討了河道斷面補償部分過流能力與諸多因素之間的關系;采用Fluent軟件建立了單墩阻水的三維數(shù)值模型,基于標準的k-?兩方程湍流模型,采用有限體積法對流體運動的控制方程進行離散、VOF方法進行自由面追蹤、壁面函數(shù)法求解壁面區(qū)流動,分析了不同工況下的河道水流特性及斷面補償部分過流能力,并與試驗結(jié)果進行了對比,得到如下主要結(jié)論:(1)對橋墩周邊水流結(jié)構(gòu)試驗表明,橋墩周邊水流的紊動具有各向異性的特點,L4測線處,橫向紊動強度*u、縱向紊動強度*v自水面向下隨著水深的增加,呈現(xiàn)逐漸增大的趨勢,在近壁面附近達到最大值,然后又逐漸減小。不同方向上的雷諾切應力沿垂向分布差別較大,其分布形態(tài)與正弦曲線相似,但變化幅度具有一定的差異。(2)對橋墩上游最大壅水高度進行分析表明,采取斷面補償措施可有效降低上游最大壅水高度,壅水高度降低程度與斷面補償面積呈正相關。斷面補償作用對橋墩處流場的影響比較明顯,進行斷面補償后,河床面上橋墩附近水流的縱向流速xV、橫向流速yV、及動水壓力均有不同程度的降低。(3)無論采取何種斷面補償型式,斷面補償部分通過的流量Q與斷面補償面積呈正相關,即隨著斷面補償面積的增大而增大。采取切灘補償方式時,切灘坡比對過流能力的影響卻并不顯著。采用疏浚方式進行斷面補償時,邊坡系數(shù)為3時斷面補償部分通過的流量最大,過流能力隨疏浚寬深比的增大,呈先減小后增大的趨勢。
[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.
【學位授予單位】：合肥工業(yè)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：U442.3

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