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1、 外文原文 Experiments in Fluids 27 (1999) 339—350 Springer-Verlag 1999 Underflow of standard sluice gate A. Roth, W. H. Hager 1. Introduction Gates are a hydraulic structure that allows regulation of an upstream water elevation.

2、 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

3、 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 re

4、garding 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) Bott

5、om 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 knowledge The present knowledge on gates was recently summarized by Lewin (1995). There is a short chapter on vertical ga

6、tes 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

7、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-nema

8、nn (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

9、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- an

10、d 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 C0.59

11、5. 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

12、 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

13、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 Humphr

14、ies (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.

15、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.

16、 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 distrib

17、utions, 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 Experiments The experiments were conducted in a 500 mm wide and 7 m long horizontal and rec

18、tangular 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 for visualization. To improve the approach flow conditions, screens were inserted and surface wav

19、es 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

20、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

21、 gate flow was considered. The gate opening was varied from a10—120mm. 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 su

22、rface 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 deter

23、mined 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

24、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 wave

25、s, and the velocity and pressure characteristics in the gate vicinity. These items are discussed in the following. 中文翻譯 標準閘門的底流 達羅斯，WH海格 流體實驗27 （1999）339-350 施普林格出版社 1999年 1．導言 閘門是一種可以控制上游水位高程的的水工建筑物。在大量的閘門設計中，配備有垂直門結構的結構被叫做標準閘門，這種閘門包含一個在有幾乎橫向平穩(wěn)矩形通道的低水頭設計中具有特別顯著作用的一個標準的波峰位置。渠道和閘門的表面粗糙度都很小，因

26、此在設計重的作用微不足道，很少為人們在設計中考慮。標準閘門經常被應用在實驗室、灌溉渠道、大型污水渠，或在其他水工建筑物上。然而與溢流結構，或者普通的堰流結構相比較，標準閘門極少被人們關注。就它的基本水利知識而言，很多和閘門相關聯(lián)的震動電子掃描數據卻是可以得到的。最近的關于標準閘門水流的在討論中的新文件涉及：（1）規(guī)模效應；（2）系數的修正；（3）表面的隆起的影響；（4）振動波的特性；（5）速度場；（6）閘門和門底部的壓力分布；（7）角落落渦；（8）渦強度。最近一種新穎的可以減少下游渠道振動波的設備也被人們提出來，因此可以說閘門是一種急需研究而且很有前途的研究項目。 2．目前知識 盧因最近（

27、1995）做了大量的研究，并總結了關于閘門的知識。在我們這里有一個關于垂直閘門系數的修正與收縮的章節(jié)，里面包含有大量的相關數據。這些反應了閘門的目前狀況，通過這些數據我們知道自己對閘門水流的研究還遠遠不夠。因為下溢的歷史資料是我們是可以獲得的，因此人們普遍認為垂直閘門的修正在上個世紀已經被做了深入的研究，因此已經沒有繼續(xù)深入研究的必要了。這并不是真正的實情，隨著現(xiàn)代測量的精確性提高了，一些小的工程也變得簡單，因此人們認為我們已經可以不做任何研究了。最近水閘研究的知名的成果包括布瓦洛（ 1848 ），鄭伯艾曼（1871，1880 ）的研究成果，其中載有哈伯斯特羅兄弟的實驗成果摘要（ 1890 ）

28、，吉布森（ 1920 ），赫斯特和瓦特（ 1925 ），克吳特（1932 ，1935），法爾（ 1937 ），艾斯坎德（ 1938 ），根體利尼（ 1941 ）以及斯美塔那（ 1948年） 。在以往實驗研究中，試驗的過程很不嚴禁，確切的幾何配置常常被人們胡亂的制定，而且試驗的數據也常常流失掉了，因此試驗的結果很值得懷疑。而且閘門固定的詳細數據也沒有被人們嚴謹的制定。現(xiàn)代的關于閘門水流研究被瑞加納木和蘇布曼娜引領(1967)，得出水閘的系數修正與上游和下游的水位高度有關。實驗過程中的水位深度接近實際水流流動水深，閘門的開啟以及收縮的系數修正也在試驗中被提出并被實測出。根據觀察自由水流以及淹沒水流

29、的相關的閘門開啟，得出隨著排放的增加淹沒收縮系數從0.595開始的輕微增加。對于表皮摩擦的影響，是人們根據假設或者潛在的勢的流理論和意見的偏差提出的。瑞安（1977）對垂直閘門進行了第二次研究，研究是在一個寬311㎜，閘門開度在26到101 mm的渠道上進行的。自由表空閘門部分的軸承最后得出是本質相同的。奴頭波波和凡瑞逖斯（1978）指出他們在重要的成果并公開了收縮系數以及系數修正的詳細數據。從數據中得出理論與實際數據的偏差常常是因為水流的空間結構特性，以及實驗室運用的管道往往比較細小的原因。納革（1978）觀察了一條400㎜寬，閘門開度為60 mm.的渠道.結果發(fā)現(xiàn)系數隨著相關閘門開度的增加

30、而從0.595減小到0.50. 作為對以前研究的增加，瑞安和哈普瑞斯（1982）認為自由水流的特性改變了上游垂直閘門的性質。這種渠道的寬度是311㎜，閘門開度是從25到50㎜。這些數據包含了向上游回流的區(qū)域，基地壓力的再分配區(qū)以及速度場。莫特斯（1997）提出了一種解決溢流的方法，這種方法運用投影圖和收縮系數的比較來試驗，而且辨別出誤差的產生是由于液流的粘滯性。這次研究對上游和下游表面輪廓，特別是閘門的開度進行了研究。過閘水頭損失與邊界層流的發(fā)展狀況，以及上游閘門水流的空間結構有關。這篇論文的目的是澄清幾個關于閘門水流的問題，包括：系數的修正;分水嶺；速度和壓力的重分布；以及那些最近才被人們充

31、分考慮的震動波的發(fā)展。這些結果也許會引導現(xiàn)在的數據模擬。它們的結果和成就在這兒還沒有被回顧總結。 3．試驗 這個試驗是在一個500 mm寬7米長的水平長方形渠道上進行的。相近的試驗的渠道寬度也被減縮到了245 到 350 mm。右手邊的墻體和閘底也被涂上了一層聚氯乙烯，而卻左手邊被按了玻璃以使我們能夠觀察清楚。為了提高水流的觀察條件，窗格被關閉以使表面的波浪盡量的減少。這種近似的水流就沒有了中心水頭損失，而且光滑度也經常在紊流的范圍之內。修正系數通過渠道下游V型堰流來測定，以確定$1% or $0.1 ls1那個更大一點。一個499mm寬，600mm高，10mm厚的鋁板也被運用在試驗過程中

32、，以使水流中的波峰成為2mm厚而且向下游傾斜45的標準的幾何形狀。閘門可以安裝得可以對閘底可變的開度。沒有門槽和水流密實度可以經過一個管理來測定，只有自由過閘水流被仔細考慮。閘門的開度時靈活的，從10mm到120mm。預制件的指定高度將比閘門的高度底0.1 mm，而且在閘門落成后將會被移走。與固定位置的開度測量比較，這種步驟被發(fā)現(xiàn)是比較準卻的。自由表面輪廓測量點的測量儀讀數有0.5毫米誤差。由于自由水面的渦流的存在，水流的深度只能被估讀到毫米。由于下部紊動波的影響，渦流的影響就更大了，而且估讀的誤差就增大到了2mm。讀數的位置確定為渠道的一米，誤差在5mm內。速度時用一個微型的儀表來測量，測量的8 mm的內部放大率，誤差保證在5%以內。而且，少量的微型圖像也被運用在靠近閘門的速度場中。作用在閘底和標準閘門的壓力運用壓力記來測量，誤差在2mm內。壓力計的直徑是1mm。這次試驗的目的是為了分析刻度的影響，自由束流的表面，邊角渦流的發(fā)展，振動波的決定因素以及減少和閘門附近速度和壓力的特性。這些項目在下面將被一一介紹。