本文選題：U形渠道　切入點(diǎn)：流速分布　出處：《西北農(nóng)林科技大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：河流、渠道、以及水工隧洞中具有自由表面的水流均稱為明渠水流，明渠均勻流是明渠水力計(jì)算中最基礎(chǔ)的問(wèn)題。灌溉渠系中U形渠道以其過(guò)流能力大、防滲效果好、輸沙能力強(qiáng)、抗外力性能優(yōu)越、占地面積小等優(yōu)點(diǎn)，被廣泛應(yīng)用于實(shí)際生產(chǎn)中。鑒于其廣泛應(yīng)用時(shí)間較短、過(guò)水?dāng)嗝嫘螤畹奶厥庑�、水流條件的復(fù)雜性等原因，U形渠道水力特性方面的研究不盡完善。 本文針對(duì)U形渠道在均勻流條件下進(jìn)行試驗(yàn)研究，以三種不同幾何尺寸U形渠道作為研究對(duì)象，以流量、水深、底坡等水力因素為變量，對(duì)不同水流條件下渠道流速進(jìn)行測(cè)試，分析了渠道斷面流速分布，水流紊動(dòng)特性，探究渠道流量計(jì)算的方法。通過(guò)研究得到以下主要結(jié)論： 1.根據(jù)實(shí)測(cè)流速等值線圖分析，發(fā)現(xiàn)渠道以中垂線為中心，兩側(cè)流速基本對(duì)稱，中垂線流速最大；最大流速點(diǎn)位置在水面以下，，最大流速位置在垂線0.6～0.8y/h范圍內(nèi)，底坡改變對(duì)此沒(méi)有影響。 2.通過(guò)對(duì)不同垂向流速分布公式與試驗(yàn)資料的對(duì)比分析，認(rèn)為拋物線形式和雙冪律形式均可反映流速的實(shí)際分布，二者相比較，雙冪律公式計(jì)算結(jié)果較拋物線公式計(jì)算結(jié)果誤差小，因此，垂向流速分布規(guī)律推薦使用雙冪律公式表示。 3.在各國(guó)學(xué)者橫向流速分布規(guī)律研究的基礎(chǔ)上，本文采用指數(shù)分布形式表示橫向流速分布規(guī)律，通過(guò)大量試驗(yàn)資料擬合出流速分布指數(shù)公式，確定了公式參數(shù)。 4.在建立U形渠道斷面流速分布公式的基礎(chǔ)上，提出斷面流量的計(jì)算公式，實(shí)例驗(yàn)證計(jì)算精度達(dá)到標(biāo)準(zhǔn)；同時(shí)，利用浮標(biāo)測(cè)流的思路，采用單一浮標(biāo)在渠道上進(jìn)行試驗(yàn)，給出浮標(biāo)系數(shù)，試驗(yàn)驗(yàn)證認(rèn)為浮標(biāo)法可以用于U形渠道流量測(cè)定。 5.分析不同測(cè)點(diǎn)流速脈動(dòng)過(guò)程線，發(fā)現(xiàn)其基本類似，并具有大小不同的準(zhǔn)周期。由實(shí)測(cè)資料統(tǒng)計(jì)的流速概率分布與理論正態(tài)分布計(jì)算的概率分布基本一致，可以認(rèn)為三向脈動(dòng)流速符合正態(tài)分布。 6.各垂線量測(cè)縱向、垂向水流紊動(dòng)強(qiáng)度自渠底向水面先減小后增大，縱向紊動(dòng)強(qiáng)度最大，最小紊動(dòng)強(qiáng)度不是出現(xiàn)在水面，而是低于自由水面的一定距離，垂向紊動(dòng)強(qiáng)度的變化規(guī)律與縱向紊動(dòng)強(qiáng)度變化情況類似，橫向紊動(dòng)強(qiáng)度變化幅度較小，水體動(dòng)量交換較為穩(wěn)定，縱、橫向相對(duì)紊動(dòng)強(qiáng)度接近為恒定值。 7.垂向雷諾切應(yīng)力隨水深變化比較均勻，近似為恒定值，在坐標(biāo)軸左右變化幅度較小，縱向與橫向雷諾切應(yīng)力在y/h＞0.5范圍內(nèi)近似為直線，y/h＜0.5區(qū)域內(nèi)近似為三角形分布，橫向雷諾正應(yīng)力沿水深分布比較均勻，近似為線性變化，不同測(cè)線上相同水深點(diǎn)橫向雷諾正應(yīng)力數(shù)值較為接近。
[Abstract]:The flow of rivers, channels and hydraulic tunnels with free surface is called open channel flow, and the uniform flow of open channel is the most basic problem in hydraulic calculation of open channel. It is widely used in practical production because of its advantages of strong sediment transport ability, superior external force resistance, small area, etc. In view of the particularity of its wide application time and cross section shape, The research on hydraulic characteristics of U-shaped channel is not perfect because of the complexity of flow conditions. In this paper, three kinds of U-shaped channels with different geometric sizes are taken as the research object, and the hydraulic factors such as flow rate, water depth, bottom slope are taken as variables. The flow velocity of the channel under different flow conditions is tested, the velocity distribution of the channel section and the turbulent characteristics of the channel section are analyzed, and the calculation method of the channel flow is explored. The main conclusions are as follows:. 1. According to the analysis of the measured velocity isoline, it is found that the center of the channel is the middle vertical line, the velocity of the two sides is basically symmetrical, and the maximum velocity of the vertical line is below the water level, and the maximum velocity position is within the range of 0.6 ~ 0.8yr / h of the vertical line. The bottom slope change has no effect on this. 2. By comparing different vertical velocity distribution formulas with experimental data, it is concluded that the parabola form and the double power law form can reflect the actual velocity distribution. The calculation result of double power law formula is smaller than that of parabola formula, so the vertical velocity distribution law is recommended to be expressed by double power law formula. 3. On the basis of the research on the law of lateral velocity distribution of scholars in various countries, the paper uses the exponential distribution form to express the law of transverse velocity distribution, and through a lot of experimental data fitting out the formula of velocity distribution index, determines the formula parameters. 4. On the basis of establishing the velocity distribution formula of U-shaped channel section, the calculation formula of section discharge is put forward, and the calculation precision is verified by an example. At the same time, using the train of thought of buoy to measure current, a single buoy is used to carry out the experiment on the channel. The buoy coefficient is given, and it is proved that the buoy method can be used to measure the flow of U-channel. 5. By analyzing the velocities pulsation process lines at different measuring points, it is found that they are basically similar and have different quasi-periods. The probability distribution of velocity calculated from the measured data is basically consistent with the probability distribution calculated by theoretical normal distribution. It can be considered that the three direction pulsating velocity accords with the normal distribution. 6. The vertical turbulence intensity of vertical flow decreases first and then increases from the bottom of the channel, and the maximum longitudinal turbulence intensity is observed. The minimum turbulence intensity does not appear on the water surface, but is lower than a certain distance from the free water surface. The variation law of vertical turbulence intensity is similar to that of longitudinal turbulence intensity. The change of transverse turbulence intensity is smaller, momentum exchange of water body is more stable, and the relative turbulence intensity is close to the constant value. 7. The vertical Reynolds shear stress varies uniformly with the water depth and is approximately constant, and the magnitude of the change is relatively small at the left and right of the coordinate axis. The longitudinal and transverse Reynolds shear stress is approximately a triangle distribution in the range of y / h > 0.5, which is approximately within the region of y / h < 0.5, and the vertical Reynolds shear stress is approximately a triangle distribution in the range of y / h > 0.5. The transverse Reynolds normal stress distributes uniformly along the water depth and is approximately linear. The transverse Reynolds normal stress values at the same water depth points on different measuring lines are close to each other.
【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TV133

【參考文獻(xiàn)】

相關(guān)期刊論文 前3條

1 王二平;金輝;張艷艷;關(guān)靖;曹兵;;矩形明渠流速分布特征及其在流量量測(cè)中的應(yīng)用[J];灌溉排水學(xué)報(bào);2008年04期

2 胡春宏;倪晉仁;;矩形明槽中斷面紊流流速分布規(guī)律的初步研究[J];水利水運(yùn)科學(xué)研究;1988年02期

3 劉寧;;中國(guó)水文水資源常態(tài)與應(yīng)急統(tǒng)合管理探析[J];水科學(xué)進(jìn)展;2013年02期

本文編號(hào)：1644451