掺气坎及阶面首级台阶对阶梯溢流坝水力特性影响研究

发布时间：2018-01-17 23:00

本文关键词：掺气坎及阶面首级台阶对阶梯溢流坝水力特性影响研究　出处：《昆明理工大学》2016年硕士论文　论文类型：学位论文

【摘要】：在大单宽流量和高水头的泄洪建筑物中,宽尾墩+阶梯溢流坝+消力池一体化消能工凭借其具有高效消能率和节约工程成本等优点而被广泛应用,但在实际工程实践中发现,泄流在阶梯溢流坝前几级阶梯处易产生空化现象,空化气泡沿水流移动在下游高压区破裂,固壁面易发生空蚀破坏。本文基于X电站,引用水气两相流VOF方法的RNGk-ε模型,采用几何重建方式对水气面附近进行插值以及利用PISO算法和非定常流算法对不同掺气坎及阶面首级台阶体型的一体化消能工三维流场进行数值模拟,并通过模型实验验证了数值模拟的可靠性,主要研究成果如下：1、掺气坎角度及高度对阶梯溢流坝水力特性的影响(1)不同掺气坎体型下的各方案计算水深、压强沿程分布走势一致。(2)在其他因素一定时,各方案阶梯水平及垂直近壁面平均掺气浓度C沿程略有波动但整体呈减小趋势,且在后几级阶梯处保持不变；各方案负压起始位置略有不同,且均存在由掺气浓度突变产生的负压绝对值骤增区：随着掺气坎角度的增大,掺气空腔长度、最大负压绝对值及掺气浓度C随其增大；随着掺气坎高度的增大,最大负压绝对值随之增大,掺气空腔长度及掺气浓度C随其减小(3)各方案临底流速V均沿水流移动方向逐渐减小：消能率沿水流移动方向逐渐增大,在消力池前段增幅较大,在尾坎附近增幅较小。在其他因素一定时,随着掺气坎角度的增大,相同断面临底流速V随之减小,消能率随其增大：随着掺气坎高度的减小,相同断面临底流速V随之减小,消能率随其增大。2、阶面首级台阶高度及台面角对阶梯溢流坝水力特性的影响(1)不同阶面首级台阶高度条件下和不同阶面首级台阶台面角条件下的各方案计算水深、压强沿程变化趋势一致。(2)在其他因素一定时,各方案阶梯水平及垂直近壁面掺气浓度C、阶梯水平及垂直近壁面负压分布走势一致：各方案均存在由掺气浓度突变产生的负压绝对值骤增区；随着阶面首级台阶高度的增大,最大负压绝对值随之减小,掺气空腔长度和相同断面掺气浓度随其增大；随着阶面首级台阶台面角的增大,掺气空腔长度、掺气浓度随其减小,最大负压绝对值随之增大。(3)各方案临底流速V沿水流移动方向逐渐减小；消能率沿水流移动方向逐渐增大,在消力池前段增幅较大,在尾坎附近增幅较小。在其他因素一定时,随着阶面首级台阶高度的增大,相同断面临底流速V随之减小,消能率随其增大；随着阶面首级台阶台面角的减小,相同断面临底流速V随之减小,消能率随其增大,即台面角下跌10。更利于能量的耗散。经综合分析,掺气坎角度为11.3。、高度为1m和阶面首级台阶高度为2m的过渡衔接方式较优。
[Abstract]:In the large single wide discharge and high head flood discharge buildings, the integrated energy dissipator of stepped spillway dam with wide tail pier is widely used because of its advantages of high efficiency energy dissipation rate and saving engineering cost. However, in the practical engineering practice, it is found that the cavitation is easy to occur at the several steps of the stepped spillway in front of the stepped spillway dam, and the cavitation bubble moves along the flow and ruptures in the high pressure area downstream. Cavitation erosion is easy to occur on the solid wall. In this paper, the RNGk- 蔚 model of water-gas two-phase flow VOF method is introduced based on X power station. The geometric reconstruction method is used to interpolate the water surface and the PISO algorithm and the unsteady flow algorithm are used to simulate the three-dimensional flow field of the integrated energy dissipator with different aerator and step shape. The reliability of the numerical simulation is verified by the model experiment. The main research results are as follows: 1. The influence of aerator angle and height on hydraulic characteristics of stepped spillway dam. 1) calculation of water depth under different aeration sill shapes and uniform distribution of pressure along the path. 2) when other factors are fixed, the influence of aeration angle and height on hydraulic characteristics of stepped spillway dam is discussed. The average aeration concentration C along the horizontal and vertical wall of each scheme fluctuates slightly but decreases as a whole and remains unchanged at the later steps. The starting position of negative pressure in each scheme is slightly different, and there is a sharp increase region of negative pressure absolute value caused by the sudden change of aeration concentration: with the increase of aeration angle, the length of aeration cavity is increased. The maximum negative pressure absolute value and aeration concentration C increase with it. With the increase of aeration height, the absolute value of maximum negative pressure increases. With the decrease of aeration cavity length and aeration concentration C) the flow velocity V of each scheme gradually decreased along the direction of flow movement; the energy dissipation rate gradually increased along the direction of water flow and increased greatly in the front section of stilling pool. When other factors are fixed, with the increase of aeration angle, the bottom velocity V of the same fault decreases, and the energy dissipation rate increases with the increase of aeration height. The bottom velocity V of the same fault decreases and the energy dissipation rate increases with it. The influence of step height and Mesa Angle on hydraulic characteristics of stepped Spillway Dam (1) the calculation of water depth under the condition of different step height and different step angle. The variation trend of pressure along the course is the same. (2) when other factors are fixed, the aeration concentration C of each scheme is horizontal and vertical near the wall. The distribution of negative pressure on the horizontal and vertical wall is the same: there is a sharp increase in the absolute value of negative pressure caused by the sudden change of aeration concentration in each scheme. With the increase of the step height of the first step, the absolute value of the maximum negative pressure decreases, and the aeration cavity length and the aeration concentration of the same section increase with it. With the increase of the angle of the first step of the step, the length of the aeration cavity and the aeration concentration decrease with it, and the absolute value of the maximum negative pressure increases with the increase of the absolute value of the maximum negative pressure. The energy dissipation rate increases gradually along the direction of water flow. The increase is larger in the front section of the stilling pool and smaller in the vicinity of the tail ridge. When other factors are fixed, with the increase of step height of the first step of the step. The bottom velocity V of the same fault decreases and the energy dissipation rate increases with it. With the decrease of the bench angle of the first step of the step, the bottom velocity V of the same fault decreases, and the energy dissipation rate increases with it, that is, the table angle decreases by 10. It is more favorable for energy dissipation. The transition connection mode is better when the aeration angle is 11.3.The height is 1m and the step height of the first step is 2m.
【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TV652.1;TV135.2

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