【摘要】：渠系分流口區(qū)域作為渠系水道的咽喉要道,對分流分沙具有重要的作用,受邊界控制,水流結構復雜。在前人研究的基礎上,本文基于南亞某待建泵站取水工程,采用理論分析,模型試驗和數(shù)值模擬相結合的方法,對不同運行工況時,渠系分流口區(qū)域的水流要素及流場特征等相關問題開展了研究,主要成果如下:1.提出研究分流口區(qū)域流場特征的意義,指出分汊流運動的復雜性,回顧了分汊流相關研究歷史和現(xiàn)狀以及分汊河道水流運動的規(guī)律,論述了數(shù)值模型研究進展及在分汊流計算應用現(xiàn)狀。2.結合多組試驗工況,對分流口區(qū)域上下游干渠段、摻混區(qū)和支渠段的三維流場特征進行研究,得出了如下規(guī)律:對于上下游干渠段水流,橫向自右岸至其與口門近區(qū)交界線,流速不斷遞減,右岸為河道的主流速帶,上下游干渠段沿縱向受渠道取水的影響不大;摻混區(qū)存在很明顯的水流混摻現(xiàn)象,口門交界面處流速梯度較大,流場三維特征明顯;水流進入引水支渠后,在支渠左岸形成一定范圍的平面回流,支渠內斷面收縮,水動力軸線集中在明渠前進方向右岸一側,形成較為明顯的螺旋流。經(jīng)過引水支渠前端復雜摻混流動區(qū)域,水流形態(tài)逐步過渡為一維特征較為明顯的常規(guī)明渠流動。3.根據(jù)室內模型試驗水流運動現(xiàn)象的觀測,利用RNGk-ε紊流模型并借助FLOW-3D軟件,建立了分流角為73°時渠系分流口區(qū)域的水力特性分析的計算模型。通過數(shù)值模擬結果與試驗結果的對比分析,驗證了該分析計算模型的準確性和可靠性。以所建立的數(shù)學模型為分析計算平臺,對于渠系分流口近區(qū)以及口門斷面不同工況多個水力要素進行了分析。重點探究三維流速沿水深的變化規(guī)律:在引水明渠前端形成的平面回流隨水深加大有減小趨勢�？陂T斷面處存在明顯的三維特征,流速分布也較常規(guī)明渠水流特征有所不同。4.引入單寬流量比的概念,重點介紹了不同單寬流量比的情況下,渠系分流口區(qū)域回流區(qū)的長度與寬度及引水支渠進水斷面收縮系數(shù)的變化規(guī)律,并推出擬合公式。分析結果表明:隨單寬流量比的增大,分流口區(qū)域回流區(qū)范圍增大,支渠渠道進水斷面收縮系數(shù)減小。
[Abstract]:As the main throat of canal system channel, the diversion area of canal system plays an important role in the separation of sediment and is controlled by the boundary, and the structure of water flow is complex. On the basis of previous studies, this paper, based on the water intake project of a pump station to be built in South Asia, adopts the method of combining theoretical analysis, model test and numerical simulation. The main results are as follows: 1. The significance of the study on the characteristics of the flow field in the diversion channel is presented, and the complexity of the branching flow is pointed out. The history and present situation of the research on the bifurcation flow and the law of the flow movement in the branching channel are reviewed. The research progress of numerical model and its application in bifurcation flow calculation are discussed. Combined with multiple test conditions, the three-dimensional flow field characteristics of upstream and downstream main canal, mixing area and branch channel in the diversion channel region are studied. The following laws are obtained: for the upstream and downstream main canal section, the flow is transversely from the right bank to the junction line between the upper and lower main channel and the adjacent area of the mouth gate. The flow velocity is decreasing, the right bank is the mainstream velocity zone of the river, the upstream and downstream main channel section is not affected by the channel water intake along the longitudinal, the mixing area has obvious mixing phenomenon, the velocity gradient at the interface of the mouth door is larger, and the three-dimensional characteristics of the flow field are obvious. After the flow enters the branch canal, a certain range of plane return is formed on the left bank of the branch canal, the cross section of the branch canal shrinks, and the hydrodynamic axis is concentrated on the right bank of the forward direction of the open channel, forming a more obvious spiral flow. Through the complex mixing flow area at the front end of the diversion branch canal, the flow pattern is gradually transformed into the conventional open channel flow with obvious one-dimensional characteristics. According to the observation of flow motion in indoor model test, using RNGk- 蔚 turbulence model and FLOW-3D software, a calculation model of hydraulic characteristic analysis of diversion outlet region of canal system is established when the diversion angle is 73 擄. The accuracy and reliability of the model are verified by comparing the numerical simulation results with the experimental results. Based on the established mathematical model, several hydraulic factors are analyzed in the near region of the diversion port of canal system and the section of the portal under different working conditions. The change rule of 3D velocity along the water depth: the plane reflux formed in the front end of the diversion channel has a decreasing trend with the increase of the water depth. There are obvious three-dimensional characteristics at the entrance section, and the velocity distribution is different from that of the conventional open channel. In this paper, the concept of single width flow ratio is introduced, and the variation law of the length and width of the reflux region in the diversion channel and the shrinkage coefficient of the inlet section of the diversion branch canal under different single width flow ratio are introduced, and the fitting formula is deduced. The results show that with the increase of the ratio of single width to flow, the range of reflux area increases and the shrinkage coefficient of inlet section decreases.
【學位授予單位】：西北農林科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TV133

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