【摘要】：突擴(kuò)水躍是閘下出流一種常見的水躍形式,多見于平原地區(qū)閘泵合建樞紐布置(中間水閘兩側(cè)泵站)和多孔閘中部分閘孔開啟泄流工況。水流由較狹窄的寬度突然擴(kuò)散,渠道下游水面寬度的突然增大必然導(dǎo)致在突擴(kuò)段產(chǎn)生回流,回流漩渦與水躍主流之間形成強(qiáng)烈的紊動(dòng)剪切層,并且回流造成對(duì)水躍主流的擠壓,使得下游單寬流量增大,形成一種復(fù)雜空間流態(tài)。本文以平底突然擴(kuò)散渠道為研究對(duì)象,通過分析前人的突擴(kuò)渠道水工模型試驗(yàn)研究成果,在自己的理論觀點(diǎn)上,分析研究了各種水力條件下平底突擴(kuò)的流態(tài)特征和基本參數(shù)。取得如下結(jié)論:(1)探究上下游渠道擴(kuò)散比對(duì)水躍共軛水深、水躍長(zhǎng)度以及水躍消能率等影響的規(guī)律。提出了一種新的突擴(kuò)渠道水躍共軛水深計(jì)算的方法;(2)通過量綱分析的p定理得出影響擴(kuò)散渠道的水躍長(zhǎng)度的因素,并擬合出突擴(kuò)渠道水躍長(zhǎng)度計(jì)算公式;(3)提出了關(guān)于平底突擴(kuò)水躍消能率計(jì)算公式,通過應(yīng)用消能率計(jì)算公式分析現(xiàn)有資料,得到擴(kuò)散渠道的消能率相對(duì)于棱柱型渠道會(huì)增加5%~10%。同時(shí),(4)應(yīng)用FLOW-3D軟件,采用數(shù)值模擬方法對(duì)平底突擴(kuò)斷面渠道內(nèi)水流進(jìn)行仿真計(jì)算,選用盧士強(qiáng)突擴(kuò)水躍試驗(yàn)?zāi)Ｐ?分別對(duì)擴(kuò)散比ε=1.2、1.5、2.0、3.0及閘孔開度ε=0.02m、0.03m、0.05m共計(jì)十二個(gè)工況水流流速及其分布形態(tài)進(jìn)行模擬分析。并對(duì)突擴(kuò)口下游渠道內(nèi)的水流流速及其分布形態(tài)進(jìn)行分析。選取閘門開度ε=0.02m,擴(kuò)散比ε=2.0和ε=3.0兩種擴(kuò)散比模擬結(jié)果分析,擴(kuò)散比ε=2.0時(shí),主流在下游擴(kuò)散渠道中較穩(wěn)定,兩側(cè)擴(kuò)散區(qū)內(nèi)的豎軸回流旋渦沿主流近似對(duì)稱;擴(kuò)散比ε=3.0時(shí),主流在下游擴(kuò)散渠道中很不穩(wěn)定,兩側(cè)的回流區(qū)并不對(duì)稱,而且主流末端還會(huì)產(chǎn)生多個(gè)小回流區(qū)。擴(kuò)散比較大時(shí),主流受到兩側(cè)豎軸旋滾擠壓,主流末端容易擺動(dòng),使得主流偏離對(duì)稱軸而發(fā)生不對(duì)稱水躍。且擴(kuò)散比越大,小回流區(qū)越多,主流擴(kuò)散越不均勻,擺動(dòng)越劇烈。本文提取了擴(kuò)散比ε=1.2、1.5、2.0三個(gè)擴(kuò)散比狀態(tài)下模擬的部分流速值,并對(duì)其進(jìn)行分析,初步探究了突擴(kuò)渠道水躍下游水流流速及流態(tài)。
[Abstract]:The sudden expansion of water jump is a common form of water jump under the gate. It can be seen in the design of the gate pump in the plain area (the pump station on both sides of the intermediate water gate) and some of the gate holes in the multi-hole gate to open the discharge working condition. the sudden increase in the width of the downstream water surface of the channel inevitably leads to the formation of a strong turbulent shear layer between the back flow, the reflux vortex and the water jump in the process expansion section, and the backflow causes an extrusion of the main flow of the water, so that the downstream single-width flow is increased, A complex spatial flow regime is formed. In this paper, a flat-bottom sudden diffusion channel is used as the research object, and through the analysis of the research results of the hydraulic model test of the pre-expansion channel of the predecessors, the fluid flow characteristics and basic parameters of the flat-bottom sudden expansion under various hydraulic conditions are analyzed. The following conclusions are obtained: (1) To explore the law of the influence of the diffusion ratio of the upstream and downstream channels on the water depth, the length of the water jump and the energy efficiency of the water jump. In this paper, a new method for calculating the water-jump length of the diffusion channel is proposed. (2) The factors influencing the water-jump length of the diffusion channel are obtained by the p-theorem of the dimensional analysis, and the calculation formula of the water-jump length of the expansion channel is fitted. (3) The formula for calculating the energy dissipation rate of the flat-bottom sudden expansion water is proposed, and the energy dissipation rate of the diffusion channel is increased by 5-10% with respect to the prism-type channel by using the calculation formula of energy dissipation rate to analyze the existing data. At the same time, (4) using the FLOW-3D software, the numerical simulation method is adopted to simulate the water flow in the channel of the flat-bottom sudden expansion section, and the Luz strong process expansion and water jump test model is selected, and the diffusion ratio of the channel is equal to 1.2, 1.5, 2.0, and 3.0 and the opening degree of the gate hole is equal to 0.02 m and 0.03m, respectively. The flow velocity of water and its distribution in a total of twelve working conditions were simulated and analyzed. The flow velocity and distribution of the water flow in the downstream channel of the flare were analyzed. The results show that the main flow is more stable in the downstream diffusion channel, and the vertical axis reflux vortex in both sides of the diffusion area is approximately symmetrical along the main flow, and the diffusion ratio is equal to 3.0. The main flow is very unstable in the downstream diffusion channel, and the return areas on both sides are not symmetrical, and a plurality of small return areas are also generated at the main end of the main flow. When the diffusion is large, the main flow is pressed by the vertical shaft on the two sides, and the main flow end is easy to swing, so that the main flow deviates from the axis of symmetry and is asymmetric water jump. And the larger the diffusion ratio, the more the small return area, the more uneven the main flow, and the more violent the swing. In this paper, the flow velocity and the flow regime of the water flow downstream of the sudden expansion channel are studied.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TV133

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