基于不同抛物线方程泄洪洞体型的试验及数值模拟研究
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摘要
水利工程中,泄水建筑物底坡变化较大,高程需急剧降低时,常采用渥奇曲线衔接上下游,以避免水流脱离底板发生空蚀,如明流泄洪洞、坝身泄水孔出口处等,此时渥奇段起着承上启下,平顺水流的作用。工程设计中,渥奇段常设计成抛物线形式,抛物线方程系数根据经验及工程重要程度选定,具有较大的不确定性。由于受水流离心力作用,渥奇段形状对溢流面的压力及流速分布有较大影响,若选择不合理容易引起不良水力现象发生。因而,研究合理渥奇段体型,有着重要的实际意义。
渥奇段在泄洪洞中得到了最广泛的应用,泄洪洞研究中,许多重要的数据都由原型观测、水工模型试验得来,但原型观测限制条件较多,水工模型试验亦有许多不足之处。随着计算机技术及计算流体力学理论的发展,数值模拟越来越多地应用于泄洪洞研究上。相比模型试验,数值模拟计算不仅可以节省大量时间、资金,还可以提供翔实的数据、资料,更可以不必考虑缩尺影响,直接对原型进行模拟计算。
本文利用水工模型试验、数值模拟技术,结合理论分析,对渥奇段体型进行了研究,得到了揭示泄洪洞水头、单宽流量与渥奇曲线系数关系的经验公式,主要研究内容包括以下几个方面:
首先,借助模型试验对某电站泄洪洞原体型泄流能力、渥奇曲线壁面压力等进行研究,得到了准确的数据,通过试验及理论分析指出原体型存在的不合理之处,并有针对性的进行了体型优化试验;
其次,通过数值模拟对泄洪洞优化体型水流流态、壁面压力进行了模拟研究,数值模拟的结果与模型实验实测数据吻合良好,说明本文采用的数值计算方法真实可靠。利用数值模拟计算得到了不同水头、单宽流量下的临界渥奇系数,指出根据临界渥奇系数原理选择渥奇系数的意义所在;
最后,利用刚体抛物理论,对水平及俯冲射流进行了分析,推导出了自由射流水舌运动轨迹方程,初步分析确定了影响渥奇段体型的因素。搜集国内泄洪洞渥奇段方程、设计水头、流量等数据,结合模型试验及数值计算成果,分析拟合得到了可用于渥奇系数选择的经验公式,经与工程实际选用的渥奇系数比较,证明本文公式具有较高的准确度。
In the hydraulic engineering, when the base plate changes greatly in the water release structure and the elevation has to reduce suddenly, we often use Ogee surface to connect the upstream and downstream to prevent the occurrence of cavitations, such as the spillway tunnel, bottom discharge orifice and so on. Actually, in these circumstances, Ogee surface plays the role as smoothing the water flow. Meanwhile, in Engineering design, Ogee surface is designed as parabolic form usually, but whose coefficient, based on the experience and the importance of selected works, shows great uncertainty. With the influence of Centrifugal force, the shape of Ogee surface affects the pressure of spillway surface and the distribution of velocity in a large degree, which may cause adverse hydraulic phenomenon if designed unreasonably. Thus, it is considered as a significant practical work on developing a reasonable Ogee section.
Ogee surface has been widely used in the discharge tunnel, many important data are derived from prototype observation and hydraulic model tests during researches. While, there are many restrictive conditions of prototype observation, hydraulic model test has a number of deficiencies too. However, with the development of computer technology and the theory of computational fluid dynamics, numerical simulation has been applied on the research of discharge tunnel more than before. Compared with model test, numerical simulation not only save much time and fund, but also provides detailed data and information, moreover, numerical simulation can simulate the prototype directly, taking the scale effect out of account.
This paper systematically study the Ogee surface, and gives empirical formula, which shows the relationship between head, unit discharge and Ogee coefficient with the help of hydraulic model tests, numerical simulation technology and theoretical analysis. The main contents of this paper include the following aspects:
Firstly, it takes model test to research on the discharge tunnel’s original body discharge capacity and Ogee surface pressure of one power plant and obtains accurate data. Then, with practical experiment and theoretical analysis it points out the unreasonable designs of the original body and tests body optimization experiment specifically;
Secondly, it simulates on the optimal size spillway’s flow pattern and wall pressure of the discharge tunnel by means of numerical simulation, the results is well consistent with the measured data obtained from the model experiment, which proves that the methodology of numerical methods is reliable. Next, it calculates the critical Ogee coefficient under different heads and unit discharge condition, and emphasizes the significance of selecting the actual Ogee coefficient according to the critical Ogee coefficient;
Finally, using rigid parabolic theory, it analysis the level and diving jet, derives the trajectory equation of free jet, and preliminary identify the factors affecting on the Ogee segment size.It collects many data about discharge tunnel parabolic equation, head, flow rate etc, around our country, combining model tests and the results of numerical simulations, through analysis as well as simulating, getting empirical formula which can be used to select fitted Ogee coefficient. Compared with the selected Ogee coefficient in actual project, it proves this formula is of high accuracy.
渥奇段在泄洪洞中得到了最广泛的应用,泄洪洞研究中,许多重要的数据都由原型观测、水工模型试验得来,但原型观测限制条件较多,水工模型试验亦有许多不足之处。随着计算机技术及计算流体力学理论的发展,数值模拟越来越多地应用于泄洪洞研究上。相比模型试验,数值模拟计算不仅可以节省大量时间、资金,还可以提供翔实的数据、资料,更可以不必考虑缩尺影响,直接对原型进行模拟计算。
本文利用水工模型试验、数值模拟技术,结合理论分析,对渥奇段体型进行了研究,得到了揭示泄洪洞水头、单宽流量与渥奇曲线系数关系的经验公式,主要研究内容包括以下几个方面:
首先,借助模型试验对某电站泄洪洞原体型泄流能力、渥奇曲线壁面压力等进行研究,得到了准确的数据,通过试验及理论分析指出原体型存在的不合理之处,并有针对性的进行了体型优化试验;
其次,通过数值模拟对泄洪洞优化体型水流流态、壁面压力进行了模拟研究,数值模拟的结果与模型实验实测数据吻合良好,说明本文采用的数值计算方法真实可靠。利用数值模拟计算得到了不同水头、单宽流量下的临界渥奇系数,指出根据临界渥奇系数原理选择渥奇系数的意义所在;
最后,利用刚体抛物理论,对水平及俯冲射流进行了分析,推导出了自由射流水舌运动轨迹方程,初步分析确定了影响渥奇段体型的因素。搜集国内泄洪洞渥奇段方程、设计水头、流量等数据,结合模型试验及数值计算成果,分析拟合得到了可用于渥奇系数选择的经验公式,经与工程实际选用的渥奇系数比较,证明本文公式具有较高的准确度。
In the hydraulic engineering, when the base plate changes greatly in the water release structure and the elevation has to reduce suddenly, we often use Ogee surface to connect the upstream and downstream to prevent the occurrence of cavitations, such as the spillway tunnel, bottom discharge orifice and so on. Actually, in these circumstances, Ogee surface plays the role as smoothing the water flow. Meanwhile, in Engineering design, Ogee surface is designed as parabolic form usually, but whose coefficient, based on the experience and the importance of selected works, shows great uncertainty. With the influence of Centrifugal force, the shape of Ogee surface affects the pressure of spillway surface and the distribution of velocity in a large degree, which may cause adverse hydraulic phenomenon if designed unreasonably. Thus, it is considered as a significant practical work on developing a reasonable Ogee section.
Ogee surface has been widely used in the discharge tunnel, many important data are derived from prototype observation and hydraulic model tests during researches. While, there are many restrictive conditions of prototype observation, hydraulic model test has a number of deficiencies too. However, with the development of computer technology and the theory of computational fluid dynamics, numerical simulation has been applied on the research of discharge tunnel more than before. Compared with model test, numerical simulation not only save much time and fund, but also provides detailed data and information, moreover, numerical simulation can simulate the prototype directly, taking the scale effect out of account.
This paper systematically study the Ogee surface, and gives empirical formula, which shows the relationship between head, unit discharge and Ogee coefficient with the help of hydraulic model tests, numerical simulation technology and theoretical analysis. The main contents of this paper include the following aspects:
Firstly, it takes model test to research on the discharge tunnel’s original body discharge capacity and Ogee surface pressure of one power plant and obtains accurate data. Then, with practical experiment and theoretical analysis it points out the unreasonable designs of the original body and tests body optimization experiment specifically;
Secondly, it simulates on the optimal size spillway’s flow pattern and wall pressure of the discharge tunnel by means of numerical simulation, the results is well consistent with the measured data obtained from the model experiment, which proves that the methodology of numerical methods is reliable. Next, it calculates the critical Ogee coefficient under different heads and unit discharge condition, and emphasizes the significance of selecting the actual Ogee coefficient according to the critical Ogee coefficient;
Finally, using rigid parabolic theory, it analysis the level and diving jet, derives the trajectory equation of free jet, and preliminary identify the factors affecting on the Ogee segment size.It collects many data about discharge tunnel parabolic equation, head, flow rate etc, around our country, combining model tests and the results of numerical simulations, through analysis as well as simulating, getting empirical formula which can be used to select fitted Ogee coefficient. Compared with the selected Ogee coefficient in actual project, it proves this formula is of high accuracy.
引文
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[2]郭军,张东,刘之平等,大型泄洪洞高速水流的研究进展及风险分析,水利学报,2006,37(10):1193-1198
[3]董志勇,吕阳泉,居文杰等,高速水流空化区和空蚀区掺气特性的试验研究,水力发电学报,2006,25(4):62-65,28
[4]李玲,陈永灿,李旭东,泄洪隧洞防空蚀体型的数值研究,水利学报,2003,(7):12-15
[5]潘家铮主编,水工隧洞和调压室——水工隧洞部分,北京:水利电力出版社,1990
[6]水利电力部第五工程局设计组,碧口水电站泄洪隧洞设计及初步运行,水工隧洞设计经验选编,北京:水利出版社,1981
[7]天津水利水电勘测设计研究院,SL253-2000溢洪道设计规范,北京:水利水电出版社,2000
[81]李炜,水力计算手册,北京:水利水电出版社,2006
[91]丁灼仪,肖兴斌,高水头深泄水孔体型的研究,长江科学院院报,1986,(S1):58-70
[10]韩立,李家峡水电站泄水建筑物高速水流问题研究,西北水资源与水工程,1990,1(4):14-26
[11]哈秋舲,胡维德,碧口水电站右岸“龙抬头”泄洪洞的几个水力学问题,水利水电技术,1980,(1):12-18
[12]陈忠儒,陈义东,短进水口底孔溢流面曲线的合理设计,人民长江,1998,(29):20-21
[13]侯精明,刘韩生,渥奇面压强的水力计算,人民长江,2007,38 (8):172～174
[14]侯精明,溢洪道空化数计算方法研究:[硕士学位论文],陕西;西北农林科技大学,2008
[15]水利水电科学研究院,南京水利科学研究院,水工模型试验(第二版),北京:水利电力出版社,1985
[16]陈椿庭,新中国35年来水工试验研究工作回顾,水利学报,1985,(5):18-22,87
[17]周胜,高斌,丁灼仪,三峡工程泄水深孔体形和水力特性研究,水力发电,1991,(8):65-69
[18]周赤,金峰,何勇,坝体泄洪深孔明槽段体型研究,长江科学院院报,2001,18(5):7-9
[19]刘韩生,模型试验中的阵发性不稳定流态及折冲流—李家峡水电站左底孔试验中的两个问题,陕西水力发电,1993,9(4):34-37,43
[20]周鸿汉,二滩水电站泄洪隧洞体型设计,水电站设计,1994,10(3):56-61
[21]牛争鸣,李建中,渥奇段的空化噪声与空化特性,西安理工大学学报,1997,13(2):140-145
[22]牛晋蜀,二滩2#泄洪洞龙抬头段减压模型试验研究,水电工程研究,1993,(2):13-20
[23]胡去劣,鲁布革水电站左岸泄洪洞水力学试验,水利水运科学研究,1984,(4):15-25
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