标准闸门的底流毕业设计外文翻译.doc

外文原文Experiments in Fluids 27 (1999) 339350 Springer-Verlag 1999Underflow of standard sluice gateA. Roth, W. H. Hager1. IntroductionGates are a hydraulic structure that allows regulation of an upstream water elevation. Among a wide number of gate designs, the so-called standard gate with a vertical gate structure containing a standard crest positioned in an almost horizontal smooth rectangular channel has particular significance in low head applications. Surface roughness of both the channel and the gate is small and thus insignificant. Standard gates are used both in laboratories and in irrigation channels, large sewers or in hydraulic structures. Compared to overflow structures, or in particular to the sharp-crested weir, standard gates have received scarce attention. The knowledge is particularly poor regarding the basic hydraulics, whereas studies relating to vibration of these gates are available. The present project describes new findings on standard gate flow, involving: (1) Scale effects; (2) Coefficient of discharge; (3) Surface Ridge; (4) Features of shock waves; (5) Velocity field; (6) Bottom and gate pressure distributions; (7) Corner vortices; and (8) Vortex intensities. A novel device to reduce shock waves in the downstream channel is also proposed.2. Present knowledgeThe present knowledge on gates was recently summarized by Lewin (1995). There is a short chapter on vertical gates containing some information on discharge and contraction coefficients,with a relatively large scatter of data. This reflects the present state, and gate flow is far from being understood from this point of view, therefore. Historical studies on underflow gates are available, and it is currently a common belief that the discharge character is tics of vertical gates have been detailed in the past century. This is definitely not the case, because of the accuracy of discharge measurement, and the small hydraulic models often used. Well known approaches include those of Boileau (1848), Bor-nemann (1871, 1880), containing summaries of the experiments of Lesbros et al. Haberstroh (1890), Gibson (1920),Hurst and Watt (1925), Keutner (1932, 1935), Fawer (1937),Escande(1938), Gentilini(1941), and Smetana(1948). In these historical experimental studies, the exact geometrical configurations are often poorly specified, and the data are not always available. Details of gate fixation are also not described. The first modern study relating to free gate flow was conducted by Rajaratnam and Subramanya (1967). The coefficient of discharge was related to the difference of flow depths in the up- and downstream sections hCa, where o c h approach flow depth, coefficient of contraction and o c agate opening. According to observations for both free and submerged flow C is exclusively a function of the relative gated opening a/h , and C increases slightly as a/h increases,o d o starting from C0.595. The effect of skin friction was stated d to be there as on for deviations between computations based on the potential flow theory and observations. Rajaratnam (1977) conducted a second study on vertical gates in a rectangular channel 311mm wide, with gate openings between 26 and 101 mm. The axial free surface profile downstream of the gate section was shown to be self-similar. Nout sopoulos and Fanariotis (1978) pointed at the significant scatter of data relating to both coefficients of contraction and discharge. The deviations between observations and theory were attributed to the spatial flow characteristics, and the channels too small often used in laboratories. Nago(1978) made observation sina400 mm wide rectangular channel with a gate opening of 60 mm. C was found to decrease with increasing relative gate opening, from 0.595 for a/h 0 to 0.52 for a/h0.50.o o.Rajarat namand Humphries (1982) considered the free flow characteristics upstream of a vertical gate, as an addition to previous studies. The channel used was 311mm wide, and gate openings were a25 and 50 mm. Their data refer to the up stream recirculation zone, the bottom pressure distribution, and the velocity field. Montes (1997) furnished a solution for the 2D outflow using conformal mapping, compared the coefficient of contraction with experiments, and identified deviations due to viscosity effects. The surface profiles up and downstream rom the gate section were studied, exclusively in terms of gate opening. Energy losses across a gate were related to the boundary layer development and the spatial flow features upstream from the gate. The pur- pose of this paper is to clarify several points of standard gate flow, including the discharge coefficient, the ridge position, the velocity and pressure distributions, and the shock wave development that was not at all considered up till now. These results may attract and guide numerical modelers of flow. Their results and approaches have not been reviewed here.3 ExperimentsThe experiments were conducted in a 500 mm wide and 7 m long horizontal and rectangular channel. The width of the approach channel was also reduced to b245 and 350mm.The right hand side wall and the channel bottom were coated with PVC, and the left hand side was of glass to allow forvisualization. To improve the approach flow conditions, screens were inserted and surface waves were adequately reduced. The approach flow was thus without flow concentrations, smooth and always in the turbulent smooth regime. The discharge was measured with a V-notch weir located down-stream of the channel, to within $1% or $0.1 ls1,whichever was larger. An aluminum gate 499mm wide, 600mm high and 10 mm thick was used, of which the crest was of standard geometry, i.e. 2mm thick with a 45° bevel on the downstream side. The gate could be mounted with variable openings from the channel bottom. No gate slots were provided and water tightness was assured with a conventional tape. Only free gate flow was considered. The gate opening was varied from a10120mm. Prefabricated elements of a specified height ($0.1 mm) were slid below the gate, and removed after the gate was positioned. This procedure was found to be accurate compared to the opening measurement of a positioned gate. Free surface profiles were measured with a point gage of $0.5 mm reading accuracy. Due to free surface turbulence, flow depths could be read only to the nearest mm. For the shock waves described below, turbulence effects were larger, and the reading accuracy was within $2 mm. The reading position was determined with a meter along the channel; to within $5 mm. Velocities were measured with a miniature propeller meter of 8 mm internal diameter to within $5%. In addition, particle image velocimetry (PIV) was used to determine the velocity field in the vicinity of the gate section. Pressure heads on the channel bottom and on the standard gate were measuredwithamanometer, towithin$2 mm. The diameter of the pressure tapings was 1mm.The experimental program aimed at analyzing the effects of scale, the free surface profile, the development of corner eddies, the determination and reduction of shock waves, and the velocity and pressure characteristics in the gate vicinity. These items are discussed in the following.中文翻译标准闸门的底流达·罗斯，W·H·海格流体实验27 （1999）339-350 施普林格出版社 1999年待添加的隐藏文字内容21导言闸门是一种可以控制上游水位高程的的水工建筑物。在大量的闸门设计中，配备有垂直门结构的结构被叫做标准闸门，这种闸门包含一个在有几乎横向平稳矩形通道的低水头设计中具有特别显着作用的一个标准的波峰位置。渠道和闸门的表面粗糙度都很小，因此在设计重的作用微不足道，很少为人们在设计中考虑。标准闸门经常被应用在实验室、灌溉渠道、大型污水渠，或在其他水工建筑物上。然而与溢流结构，或者普通的堰流结构相比较，标准闸门极少被人们关注。就它的基本水利知识而言，很多和闸门相关联的震动电子扫描数据却是可以得到的。最近的关于标准闸门水流的在讨论中的新文件涉及：（1）规模效应；（2）系数的修正；（3）表面的隆起的影响；（4）振动波的特性；（5）速度场；（6）闸门和门底部的压力分布；（7）角落落涡；（8）涡强度。最近一种新颖的可以减少下游渠道振动波的设备也被人们提出来，因此可以说闸门是一种急需研究而且很有前途的研究项目。2目前知识卢因最近（1995）做了大量的研究，并总结了关于闸门的知识。在我们这里有一个关于垂直闸门系数的修正与收缩的章节，里面包含有大量的相关数据。这些反应了闸门的目前状况，通过这些数据我们知道自己对闸门水流的研究还远远不够。因为下溢的历史资料是我们是可以获得的，因此人们普遍认为垂直闸门的修正在上个世纪已经被做了深入的研究，因此已经没有继续深入研究的必要了。这并不是真正的实情，随着现代测量的精确性提高了，一些小的工程也变得简单，因此人们认为我们已经可以不做任何研究了。最近水闸研究的知名的成果包括布瓦洛（ 1848 ），郑伯·艾曼（1871，1880 ）的研究成果，其中载有哈伯斯特罗兄弟的实验成果摘要（ 1890 ），吉布森（ 1920 ），赫斯特和瓦特（ 1925 ），克吴特（1932 ，1935），法尔（ 1937 ），艾斯坎德（ 1938 ），根体利尼（ 1941 ）以及斯美塔那（ 1948年） 。在以往实验研究中，试验的过程很不严禁，确切的几何配置常常被人们胡乱的制定，而且试验的数据也常常流失掉了，因此试验的结果很值得怀疑。而且闸门固定的详细数据也没有被人们严谨的制定。现代的关于闸门水流研究被瑞加纳木和苏布曼娜引领(1967)，得出水闸的系数修正与上游和下游的水位高度有关。实验过程中的水位深度接近实际水流流动水深，闸门的开启以及收缩的系数修正也在试验中被提出并被实测出。根据观察自由水流以及淹没水流的相关的闸门开启，得出随着排放的增加淹没收缩系数从0.595开始的轻微增加。对于表皮摩擦的影响，是人们根据假设或者潜在的势的流理论和意见的偏差提出的。瑞安（1977）对垂直闸门进行了第二次研究，研究是在一个宽311，闸门开度在26到101 mm的渠道上进行的。自由表空闸门部分的轴承最后得出是本质相同的。奴头波波和凡瑞逖斯（1978）指出他们在重要的成果并公开了收缩系数以及系数修正的详细数据。从数据中得出理论与实际数据的偏差常常是因为水流的空间结构特性，以及实验室运用的管道往往比较细小的原因。纳革（1978）观察了一条400宽，闸门开度为60 mm.的渠道.结果发现系数随着相关闸门开度的增加而从0.595减小到0.50. 作为对以前研究的增加，瑞安和哈普瑞斯（1982）认为自由水流的特性改变了上游垂直闸门的性质。这种渠道的宽度是311，闸门开度是从25到50。这些数据包含了向上游回流的区域，基地压力的再分配区以及速度场。莫特斯（1997）提出了一种解决溢流的方法，这种方法运用投影图和收缩系数的比较来试验，而且辨别出误差的产生是由于液流的粘滞性。这次研究对上游和下游表面轮廓，特别是闸门的开度进行了研究。过闸水头损失与边界层流的发展状况，以及上游闸门水流的空间结构有关。这篇论文的目的是澄清几个关于闸门水流的问题，包括：系数的修正;分水岭；速度和压力的重分布；以及那些最近才被人们充分考虑的震动波的发展。这些结果也许会引导现在的数据模拟。它们的结果和成就在这儿还没有被回顾总结。3试验这个试验是在一个500 mm宽7米长的水平长方形渠道上进行的。相近的试验的渠道宽度也被减缩到了245 到 350 mm。右手边的墙体和闸底也被涂上了一层聚氯乙烯，而却左手边被按了玻璃以使我们能够观察清楚。为了提高水流的观察条件，窗格被关闭以使表面的波浪尽量的减少。这种近似的水流就没有了中心水头损失，而且光滑度也经常在紊流的范围之内。修正系数通过渠道下游V型堰流来测定，以确定$1% or $0.1 ls1那个更大一点。一个499mm宽，600mm高，10mm厚的铝板也被运用在试验过程中，以使水流中的波峰成为2mm厚而且向下游倾斜45°的标准的几何形状。闸门可以安装得可以对闸底可变的开度。没有门槽和水流密实度可以经过一个管理来测定，只有自由过闸水流被仔细考虑。闸门的开度时灵活的，从10mm到120mm。预制件的指定高度将比闸门的高度底0.1 mm，而且在闸门落成后将会被移走。与固定位置的开度测量比较，这种步骤被发现是比较准却的。自由表面轮廓测量点的测量仪读数有0.5毫米误差。由于自由水面的涡流的存在，水流的深度只能被估读到毫米。由于下部紊动波的影响，涡流的影响就更大了，而且估读的误差就增大到了2mm。读数的位置确定为渠道的一米，误差在5mm内。速度时用一个微型的仪表来测量，测量的8 mm的内部放大率，误差保证在5%以内。而且，少量的微型图像也被运用在靠近闸门的速度场中。作用在闸底和标准闸门的压力运用压力记来测量，误差在2mm内。压力计的直径是1mm。这次试验的目的是为了分析刻度的影响，自由束流的表面，边角涡流的发展，振动波的决定因素以及减少和闸门附近速度和压力的特性。这些项目在下面将被一一介绍。