【作者】 林劲松；

【导师】 吕宏兴；

【作者基本信息】 西北农林科技大学 ， 水利水电工程， 2011， 博士

【摘要】 水电站建设中涉及到的水力学问题众多。本文着重研究了水电站长引水渠道水力瞬变过程中的波涌情况、水电站尾水河道疏挖以及水电站长引(尾)水压力隧洞(管道)的水力过渡过程的基本理论和计算方法,并在实际工程中推广应用。利用建立在经物理模型验证后的数值仿真计算技术,以白龙江横丹水电站和西藏雪卡水电站为实例,进行了水电站规划设计阶段遇到的明渠非恒定流运动的仿真计算研究。在水电站尾水河道疏挖研究中,给出了复杂地形条件下天然河道水面线的计算方法;对拟建中的黄河羊曲水电站尾水疏挖进行了优化研究,在考虑龙羊峡水库不同回水高程条件下,量化计算了黄河羊曲水电站尾水疏挖最优方案的运行效果。最后将水电站水力过渡过程仿真计算应用于大、中型水电站的水力过渡过程计算,并与模型试验结果对比分析。主要结论如下:(1)在长引水渠道水力瞬变过程计算研究中,通过对白龙江横丹水电站长引水渠道波涌计算表明:白龙江横丹水电站引水发电系统总体设计是合理的,建议将渠底高程降低0.5 m,既能满足正常运行时Q=161.8 m~3/s的设计流量,又可取消侧堰工程。在雪卡水电站水力瞬变过程计算研究中,对四台机工作状况下,进行了水力瞬变计算与部分规范公式的比对。按规范计算了四台机运行时前池正常蓄水位时的水面线和前池最高水位时的水面线,而水力瞬变计算给出非恒定流出现的最高水面线及最低水面线的上下包络线,更符合水流运动的特点。水力瞬变仿真计算同时可以提供渠道进口流量、侧堰溢流过程线;渠道瞬态水面线;波涌上下游传播与反射过程等,与设计规范相比可以提供更多的信息,且更合理地描述非恒定流运动。(2)完整的一维恒定非均匀流仿真计算模型,能较好地符合天然不规则地形条件下水流的运动规律,既考虑了上下游断面间的宽度、高程变化,又反映了沿程和局部的水头损失,其结果应更贴近于实际工程。采用预测—校正求解法,应用一维恒定非均匀流仿真计算模型,增加急流的均匀流水深与临界水深判断公式,可以较好地解决天然河道复式断面正坡、倒坡交替出现,突扩、突缩频繁发生的复杂地形条件下水面线计算的连续性问题。对于复杂地形糙率系数,先预设糙率系数,经采用预测—校正求解法多次反复试算,确定羊曲峡、野狐峡峡谷段的糙率系数n=0.04,中间吾托盆地段糙率系数n=0.03,此时水面线计算结果与实测水面线资料吻合良好,所确定的糙率系数也符合工程规范和技术人员的经验。由水面线计算结果看出,虽然个别断面计算与实测的最大误差达到0.54 m,但大多数断面两者的水位误差在0.4 m以内,可满足工程设计精度要求。应用一维恒定非均匀流计算模型,拟定2种不同疏挖长度的方案,重点研究河道疏挖3 472 m,疏挖比降为0.05%、0.1%、0.15%,疏挖宽度为50 m、80 m、140 m的疏挖效果。共组合了8套疏挖地形,在每套疏挖地形上,分别预报了各级流量下的水面线、特征断面的水位～流量关系。综合分析后,推荐开挖方案Ⅱ-0.05%-50,即开挖末端到达野狐峡进口,开挖比降为0.05%,开挖宽度为50 m,开挖工程量为123.19万m~3。此时推荐方案平均流量625.0 m~3/s下,厂房尾水位由开挖前的2 595.49 m降低到2 590.34 m,降低了5.15 m;随着流量的增大,电站尾水位降低的幅度越来越小,当流量超过2 500 m~3/s以后,开挖河道电站尾水位几乎不再降低。对于给定的龙羊峡坝前水位,野狐峡断面都有相应的水位~流量关系曲线。数学模型在推荐的开挖宽度为50 m、开挖比降为0.05%的河道地形上,针对每一级龙羊峡水位,以野狐峡水位~流量关系为下边界条件,计算开挖河段不同流量下的若干条水面线成果。结果表明,龙羊峡水位很低时,羊曲河道水面线较陡,几乎不受回水顶托;当龙羊峡水位较高时,河道水面线变缓,接近水平,说明此时已完全被淹没在龙羊峡库区。在龙羊峡水库不同坝前水位时,平均流量625 m~3/s羊曲水电站尾水水位降幅为0.48 m～4.47 m。河道流量愈大,水位降幅愈小,反之亦然。(3)水电站水力过渡过程用管道一维非恒定流方程及其初边条件控制,内加调压室、串联管、分岔管、机组特性等,采用特征线法求解,其计算结果与试验资料吻合良好。该模型也用于几个电站水力过渡过程仿真计算,解决了工程设计问题。水力学仿真计算的工程应用,进一步提高了数值仿真的可信度及对物理现象的认识。更多还原

【Abstract】 There are numerous problems involved the hydraulics in the construction of a hydropower station, this paper focuses research on the basic theory and calculation method which involve the wave surge in hydraulic transient process of the long diversion channel, tail water dredging of the riverbed, hydraulic transition process of the long tail water or diversion pressure tunnel (pipe) in the hydropower station, meanwhile having been applied in practical engineerings.Based on the physical model test which is verified by the numerical simulation technology, the simulation researches on the unsteady flow in an open channel are carried out by using the examples of Hengdan Hydropower Station which is located in Bailong River and Xueka Hydropower Station in Tibet when they are in the planning design stage.The calculation method is focused on the natural river’s water surface under the condition of complex terrain. The studies on the tail water dredging in Yangqu Hydropower Station are optimized under considering the mainly optimum results in different influence of dredging under different backwater elevation of Longyangxia Reservoir which located in the Yellow River.Finally the simulation for transient flow of the long diversion channel in the hydropower station is made and the result is applied in the analysis and study for Hengdan Hydropower Station and Xueka Hydropower Station. At the same time, through the comparative analysis with the results of model experiments, the simulation calculation for hydraulic transition process is used in the large and middle hydropower stations. The main conclusions are as follows:(1) The simulation study on the wave surge of the long diversion channel in Hengdan Hydropower Station shows that the overall design is reasonable. The suggestion is proposed that the channel bottom elevation should be declined 0.5 m for meeting the design flow of 161.8m~3/s during normal operation and canceling the side weir project. The comparison between the hydraulic transient calculations and ministerial specification formulas under four machines working conditions are made in the simulation calculations for Xueka Hydropower Station.The water surface profiles under the normal condition and the highest level in impoundment pool are calculated under four machines working conditions by using the ministerial specification formulas, and the fluctuation envelopes including the highest water level and lowest water level from hydraulic transient calculation are more suitable to describe the movement of water flow, that is to say, they are more accordant with the characteristics of water flow movement. Many parameters such as the flow of channel inlet, overflow flow line of siedweir, channels’transient surface lines, and the spread and reflection processes of the upstream and downstream wave surge could be provided by hydraulic transient simulation, at the same time, compared with design code, more information could be provided, and more reasonable description could be made for unsteady flow movement.(2) The simulation calculation model for complete one-dimensional steady non-uniform flow could better accord with the flow movement rules under natural irregular topography, not only taking into account the width and elevation changes in both upstream and downstream section, but also reflecting the alongshore and local head loss, so the result should be more close to the actual project.Based on the prediction - correction solving method, the simulation calculation model for complete one-dimensional steady non-uniform flow, and the criterion formula for uniform flow depth and critical water depth, the continuity for water surface profile calculating could be resolved better under the complex terrain conditions with plus slope and adverse slope alternating and with sudden expansion and sudden contraction occurring frequently in compound section rivers. The results of the computation should be closer to reality.For the roughness coefficient of complicated terrain , the roughness coefficient should be preset firstly, Here, by using the prediction - correction method to calculate many times repeatedly, the roughness coefficient of Yangqu Gorge to Yehu Gorge is determined as 0.04 and that of Wutuo Basin is determined as 0.03. Now the water surface lines from calculation and observation are identical well, the roughness coefficients determined here are also accordant with engineering specifications and technical personnel’s experience. The water surface lines from calculation results show that although the maximum error between the calculation and observation individual sections would be 0.54 m, but in most sections, the error of the water level should be less than 0.4 m, the error could meet the accuracy for engineering design.Through the application of one-dimensional steady non-uniform flow calculation model, the plan of two different dredging lengths are proposed, and the research is focused on the dredging effects for dredging being 3472 m, slopes of river for 0.05%, 0.1%, 0.15%, dredging widths being 50 m, 80 m, 140 m. Eight sets of dredging plans are combined, and the water surface lines under various flows and the water level ~ flow relations in characteristic sections are forecasted respectively.The recommended excavation programⅡ( -0.05% -50 m) is got by comprehensive analyses, the width is 50 m and slope is 0.05%, and the amount of excavation works is 1,231,900 m~3 from the end of the excavation to the import of Yehu Gorge. Now under the average flow of 625.0 m~3/s in the recommended program, the tail-water level of the workshop is declined from 2 595.49 m to 2 590.34 m before and after the excavation, reducing 5.15 m. Along with the increase of the flow, the tail-water level of the workshop is reduced smaller and smaller, and when the flow is more than 2 500 m~3 / s, the tail-water level of the workshop is hardly decreased after the excavation.For the given water level before Longyangxia dam, there are the corresponding water level ~flow relation curves in Yehu Gorge. Aiming at each water level before the dam and with the water level ~flow relation of Yehu Gorge for the next boundary condition, the mathematical model is used to calculate the several water surface lines under different flows in the excavated river reach under the recommended excavation width of 50 m and the excavation gradient for 0.05%.The results show that when the water level of Longyangxia dam is lower, the water level of Yangqu reach is similar with the natural curved line, and is hardly affected by the backwater of Longyangxia Reservoir; when the water level of Longyangxia dam is higher, the water level of Yangqu reach is similar with the horizontal line, Yangqu reach is completely submerged in Longyangxia Reservoir.The tailrace water level is dropped for 0.48 m ~ 4.47 m with the average flow of 625 m~3/s when the water level in Longyangxia Reservoir is different. The water level is dropped smaller when the river flow is becoming greater, and vice versa.(3) The one-dimensional unsteady flow equation is used to control the transient process of water pipeline and the initial boundary conditions in a hydropower station; the characteristics of the add surge chamber in tandem tube, bifurcation pipe and the units are solved by using the feature line method, the calculation results are in good agreement with the physical model test results. This model is also used in the simulation calculations for the transition process in several hydropower stations to solve problems of hydraulic engineering design. The application of the hydraulic simulation could further improve the credibility of the numerical simulation and the understanding for the physical phenomena.更多还原