平底突扩断面渠道的水力性能研究

发布时间：2019-05-20 16:42

【摘要】：突扩水跃是闸下出流一种常见的水跃形式,多见于平原地区闸泵合建枢纽布置(中间水闸两侧泵站)和多孔闸中部分闸孔开启泄流工况。水流由较狭窄的宽度突然扩散,渠道下游水面宽度的突然增大必然导致在突扩段产生回流,回流漩涡与水跃主流之间形成强烈的紊动剪切层,并且回流造成对水跃主流的挤压,使得下游单宽流量增大,形成一种复杂空间流态。本文以平底突然扩散渠道为研究对象,通过分析前人的突扩渠道水工模型试验研究成果,在自己的理论观点上,分析研究了各种水力条件下平底突扩的流态特征和基本参数。取得如下结论:(1)探究上下游渠道扩散比对水跃共轭水深、水跃长度以及水跃消能率等影响的规律。提出了一种新的突扩渠道水跃共轭水深计算的方法;(2)通过量纲分析的p定理得出影响扩散渠道的水跃长度的因素,并拟合出突扩渠道水跃长度计算公式;(3)提出了关于平底突扩水跃消能率计算公式,通过应用消能率计算公式分析现有资料,得到扩散渠道的消能率相对于棱柱型渠道会增加5%~10%。同时,(4)应用FLOW-3D软件,采用数值模拟方法对平底突扩断面渠道内水流进行仿真计算,选用卢士强突扩水跃试验模型,分别对扩散比ε=1.2、1.5、2.0、3.0及闸孔开度ε=0.02m、0.03m、0.05m共计十二个工况水流流速及其分布形态进行模拟分析。并对突扩口下游渠道内的水流流速及其分布形态进行分析。选取闸门开度ε=0.02m,扩散比ε=2.0和ε=3.0两种扩散比模拟结果分析,扩散比ε=2.0时,主流在下游扩散渠道中较稳定,两侧扩散区内的竖轴回流旋涡沿主流近似对称;扩散比ε=3.0时,主流在下游扩散渠道中很不稳定,两侧的回流区并不对称,而且主流末端还会产生多个小回流区。扩散比较大时,主流受到两侧竖轴旋滚挤压,主流末端容易摆动,使得主流偏离对称轴而发生不对称水跃。且扩散比越大,小回流区越多,主流扩散越不均匀,摆动越剧烈。本文提取了扩散比ε=1.2、1.5、2.0三个扩散比状态下模拟的部分流速值,并对其进行分析,初步探究了突扩渠道水跃下游水流流速及流态。
[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.
【学位授予单位】：西北农林科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV133

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