本文選題：圓柱型橋墩 + 局部沖刷��； 參考：《北京交通大學(xué)》2014年碩士論文

【摘要】：橋梁墩臺局部沖刷是導(dǎo)致跨江橋梁破壞的主要原因之一,局部沖刷深度與沖刷坑形態(tài)的正確預(yù)測,是橋梁合理設(shè)計與安全運營的重要保障。由于墩周局部沖刷坑內(nèi)水流結(jié)構(gòu)復(fù)雜,泥沙輸運理論不完善以及坑內(nèi)泥沙隨機(jī)崩塌等問題,現(xiàn)有水沙耦合計算模型不能準(zhǔn)確地模擬出局部沖刷坑的演變過程,故本文通過實驗室試驗和數(shù)值計算研究了圓柱型橋墩周圍局部沖刷過程中墩周水流的變化,主要工作如下： (1)介紹了國內(nèi)外因橋墩臺局部沖刷而發(fā)生的橋梁水毀事件,結(jié)合局部沖刷的研究現(xiàn)狀,論述了局部沖刷發(fā)展過程中墩周流場變化對局部沖刷機(jī)理研究的重要性。 (2)基于計算流體力學(xué)原理,應(yīng)用Fluent中的RNGk-ε湍流模型,經(jīng)適當(dāng)?shù)谋诿嫣幚?對圓柱型橋墩局部沖刷發(fā)展過程中復(fù)雜的三維流場進(jìn)行了數(shù)值模擬。 (3)通過平床條件下試驗測量得到的墩周流速對數(shù)值模型結(jié)果準(zhǔn)確性進(jìn)行了驗證,兩者結(jié)果的一致性證明了本文方法的有效性。同時,本文對平床條件下墩周復(fù)雜的水流進(jìn)行了分析,其中數(shù)值模擬能很好地模擬出墩周的水流結(jié)構(gòu)。 (4)以實測圓柱型橋墩沖刷過程中不同時刻下的沖刷坑形態(tài)為邊界條件建立相應(yīng)數(shù)值模型,其模擬結(jié)果揭示了墩周水流流速、床面切應(yīng)力、渦量和紊動能隨沖刷過程的變化規(guī)律。 (5)根據(jù)局部沖刷試驗與不同時刻下墩周水流紊流場的分布情況,分析結(jié)果表明了墩周馬蹄渦系,加速水流及尾渦是引起局部沖刷的主要動力因素。在沖刷初期,墩側(cè)加速水流對橋墩局部沖刷起主導(dǎo)作用；隨著沖刷的發(fā)展,馬蹄渦系對沖刷的影響作用增大,與墩側(cè)加速水流作用相當(dāng)；而墩后水流一直都處于尾渦回流區(qū),流速較小,但其紊動性較強(qiáng),墩后床面泥沙沖刷主要受到尾渦和水流紊動的共同作用。
[Abstract]:The local scour of bridge pier and abutment is one of the main reasons leading to the destruction of bridge across the river. The correct prediction of local scour depth and scour pit form is an important guarantee for the rational design and safe operation of bridge. Due to the complex structure of water flow in the local scour pit around the pier, the imperfect theory of sediment transport and the random collapse of sediment in the pit, the existing coupled calculation model of water and sediment can not accurately simulate the evolution process of the local scour pit. Therefore, the changes of the flow around the piers during the local scour around the piers are studied by laboratory tests and numerical calculations. The main work is as follows: This paper introduces the events of bridge water damage caused by local scour of pier abutment at home and abroad, and discusses the importance of the variation of flow field around pier during the development of local scour to the study of local scour mechanism combined with the research status of local scour. 2) based on the principle of computational fluid dynamics, the complex three-dimensional flow field in the development of local scour of cylindrical bridge pier is numerically simulated by using RNGk- 蔚 turbulence model in Fluent and proper wall treatment. 3) the accuracy of the numerical model is verified by the circumferential velocity of the piers measured under the flat bed condition. The agreement between the two results proves the validity of the proposed method. At the same time, the complex flow around the pier under the condition of flat bed is analyzed, and the numerical simulation can well simulate the flow structure around the pier. (4) the corresponding numerical model is established based on the measured scour pit shape at different times during the scouring process of cylindrical bridge pier. The simulation results reveal the variation of flow velocity, bed shear stress, vorticity and turbulent energy with the scouring process. 5) according to the local scour test and the distribution of turbulent flow around the pier at different times, the results show that the horseshoe vortex system around the pier is the main dynamic factor that causes the local scour. In the early stage of scour, the accelerated flow at the pier side plays a leading role in the local scour of the bridge pier. With the development of scour, the effect of horseshoe vortex system on scour is increased, which is equivalent to that of the accelerating flow on the side of the pier, and the flow behind the pier is always in the wake vortex return zone. The velocity of flow is small, but its turbulence is stronger, and the sediment scouring behind the pier is mainly affected by the wake vortex and the turbulence of the flow.
【學(xué)位授予單位】：北京交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U442.3;U443.22

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