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1.
This paper reports on model studies on energy dissipatorswhich were performed with a view towards developing a shorterand more efficient type of stilling basin for circular pipeoutlets at low Froude numbers. The stilling basin models weretested for two pipe outlet diameters. The outlet Froude numberfor testing ranged from 1.70 to 5.50. The studies reported inthis paper expand on the improvement suggested by Goel andVerma (1999). In all, 133 test runs were made on 19 newmodels. Various configurations of stilling basin models withdifferent sizes, shapes and locations of appurtenances andbasin lengths were tested. The use of a wedge-shaped splitterblock, an impact wall, and the use of wedge-shaped blocks asbaffle blocks resulted in efficient energy dissipation inshorter lengths of stilling basin. A non-dimensional numbertermed as scour index has been used to compare theperformances of various stilling basin models. It was foundthat the length of stilling basin could be reducedconsiderably without affecting the performance by choosing asuitable configuration of the stilling basin. Of theconfigurations tested, the stilling basin model M-24 with tworows of wedge-shaped baffle blocks in a basin length of sixtimes the diameter of pipe outlet (6d) performed better incomparison to USBR impact type VI stilling basin. 相似文献
2.
河南省薄山水库输水道出口消力塘采用四级消能工进行消能。 由于高速水流产生的气蚀破坏,消能工遭到严重破坏。为解决此问题,进行了水工模型实验。根据实验资料,决定采用坡顶墩替代原三角形分水墩。经运行多年,消能情况良好。另外,对气蚀破坏的原因及处理改善措施作了比较完整的论述,并对高速水流消能工的设计及运行管理提出了一些建议。 相似文献
3.
Muhammad F. Bari 《Irrigation and Drainage Systems》1993,7(2):131-150
Flow conditions, which could not be explained, occurred in the stilling basin and outfall channel of the Feni Regulator sited at the western end of the Feni River closure dam. This regulator controls outflows from the upstream reservoir which supplies irrigation water to Muhuri Project in Bangladesh. Analysis of flood discharge data revealed that the design discharge for the structure was not exceeded; yet abnormal scour occurred in the outfall channel and the brick block rip-rap placed thereon was damaged. A model study was conducted to understand the causes of such unusual local erosion downstream of the stilling basin and to provide answers to two main questions: -Is potential scour serious in terms of the stability of the structure? -What protection measures could be taken to stabilize the scour at a safe level? Using a 1:30 scale model, the probable maximum scour was simulated, and the performance of alternative rip-rap designs including that of the existing one were examined. The results of this study supplemented by field scour data collected during subsequent flood seasons indicated that even if the flow rate through the regulator approaches the design flood discharge, the downstream scour is not likely to extend up to an elevation of ? 10.7 m, a scour level observed in the previous year at a lower discharge. It also showed that the existing rip-rap blocks were marginally undersized and consequently the rip-rap was prone to failure if flow conditions departed from uniform. A suitable method of scour protection downstream of the stilling basin at the regulator exit also evolved from the study. 相似文献
4.
在暖通空调的水系统中,管网型式与阻力的变化对水泵运行特性产生重要的影响.通过实例对水泵变流量运行进行计算与分析,并采用管网阻力调节、水泵台数控制及变频控制方法调节系统流量.探讨了管网变化对水泵变流量运行能耗的影响;分析了管网性质与水泵运行工况的关系,以及各种流量调节方式与水泵运行能耗的关系.计算结果表明：管网特性对水泵变流量运行的能耗影响较大.通过增加管网的阻力调节流量,通常会使水泵的能耗降低;水泵变频控制方式对开、闭式管网的运行能耗影响有较大的区别,静压值越大,节能效果越小;在闭式循环管网中,水泵台数控制与变频控制是两种有效的节能调节方法,由于管网发生变化,水泵的运行工况变化不满足相似律;水系统通过采用压差控制流量时,最不利环路可能发生变化成为次不利环路,所以末端压差控制因管网变化而形成水力失调,最小阻力控制比定压差控制有显著的节能效果. 相似文献
5.
M.A. Sekendar 《Agricultural Water Management》1984,8(4):351-360
The entrance resistance and the effective radius of corrugated PVC drain pipes without envelope and with six different prewrapped envelopes were evaluated in a sand tank experiment.By applying the theory of resistances, the entrance resistance of the naked pipe was found to be 0.0136 days/m. With envelopes, the values were 0.0024 to 0.0067 days/m, depending on the types of envelope.The effective radius of the naked pipe was found to be 0.47 cm for a drain pipe with an actual radius of 3.0 cm. This value increased to between 1.20 and 2.50 cm when envelope material was used. Then the values of the calculated entrance resistances were substituted in the steady state drainage equations under normal field conditions to evaluate the effect on drain spacing. In all equations, a tendency towards increasing the drain spacing was observed when envelope material was used. 相似文献
6.
为了探求大型灌溉管网中适用性更强的减压阀型式,提出了一种新型减压阀结构设计方案,阐述了其结构组成和工作原理.运用Gambit和CFX软件建立了阀瓣在5个开度工况下整体结构的三维模型,对阀体进行了数值模拟,分析得到了阀体的静态特性.探明了不同进口流量条件下,减压阀进出口压差变化规律和阀瓣所受驱动力变化规律,同时分析了阀体及特殊截面的压强和速度分布云图.通过模型试验测得阀瓣开度分别固定在1.0,1.6,2.4 cm时,不同进口流量条件下进出口压差值,结果表明:试验与数模结果偏差在2.8%~7.9%,数值模拟和物理模型试验结果证明结构改进设计方案是合理的.为减压阀阀体结构设计提供了理论指导,并为今后同类产品开发提供了参考依据. 相似文献
7.
我国温室产业近年来发展迅猛,由于面积、种植结构与密度等与大田差异较大,沿用大田滴灌系统的设计方法已不适宜,需要根据温室的具体条件确定设计方法。根据我国普通单栋温室情况,通过室内试验研究分析了入口压力、支管长度、毛管间距3个因素对滴灌系统中支管沿程压力分布的影响。结果表明:支管沿程压力分布的均匀性随支管长度的增加、毛管间距和首部压力的减小而降低。结合滴头的水力特性参数得出支管上的最大允许压力偏差为30.85%。毛管间距0.6、0.9和1.2m条件下,满足水力偏差要求的单栋温室支管最大铺设长度分别为20、40和60m。运用量纲分析方法将影响支管水头损失的基本量导出为3个无量纲量υd/ν、υ2/(g d)和L d/s2,通过多元回归建立支管水头损失的经验预测模型(R2=92.4%)。分析了支管能坡曲线的函数形式,回归得到了支管水头损失比和沿程压力分布模型。以上模型预测值与实测数据拟合效果良好,可用于温室滴灌系统水力计算及规划设计。 相似文献
8.
管网的布置对系统的投资有很大的影响,但管材及价格的变化使系统最佳布置不是唯一的。本文结合实例分析了系统布置与管材及价格变化之间的联系,在此基础上给出了半固定式喷灌系统设计中应加以注意的问题,并根据当前的条件推荐了几种布置形式。 相似文献
9.
根据渗流理论,结合工程实际,以不同配比的无砂混凝土管为研究对象,探讨无砂混凝土管在不同粒径滤料的颗粒级配和多种防冲层材料条件下对渗流取水效能所产生的影响和变化规律。根据试验结果可以得出：水库采用无砂混凝土管取水的能力是可观有效的,滤料颗粒继配良好,防冲层为无砂混凝土板时无砂混凝土管的渗流能力和取水效率较为理想。 相似文献
10.
通过深圳市大沙河4号橡胶坝消力池水工模型试验，获得了水流流态、河道断面流速分布等试验成果，分析了消力池左岸预制块护坡产生滑坡破坏的机理，对消力池内辅助消能工形式及布置作了比较分析，河道主流偏左、冲刷左岸现象得到控制。 相似文献
11.
曲面贴角窄缝挑坎是在直墙窄缝挑坎基础上发展而来的典型消能工,目前对曲面贴角窄缝挑坎水力特性的研究还较少。通过对比分析曲面贴角窄缝挑坎与直墙窄缝挑坎体型结构、消能机理、受力特征上的差异,并从水力模型实验方面予以验证,证实曲面贴角窄缝挑坎除具有传统窄缝挑坎的优点外,还具有边墙低、消能充分、稳定性及安全性好、水舌纵向横向较为分散、底槽水舌挑距稳定有利于跨岸、下游河道冲刷深度较浅等优点。 相似文献
12.
Total energy loss assessment for trickle lateral lines equipped with integrated in-line and on-line emitters 总被引：4，自引：3，他引：1
Gürol Yildirim 《Irrigation Science》2010,28(4):341-352
The accurate evaluation for the pressure head distribution along a trickle (drip) irrigation lateral, which can be operated
under low-pressure head, dictates to precisely determine the total energy (head) losses that incorporate the combined friction
losses due to pipe and emitters and, the additional local losses, sometimes called minor losses, due to the protrusion of
emitter barbs into the flow. In routine design applications, assessment of total energy losses is usually carried out by assuming
the hypothesis that minor losses can be neglected, even if the previous experimental studies indicated that minor losses can
become a significant percentage of total energy losses as a consequence of the high number of emitters (with reducing the
emitter spacing) installed along the lateral line. In this study, first, simple mathematical expressions for computing three
energy loss components—minor friction losses through the path of an integrated in-line emitter, the local pressure losses
due to emitter connections, and the major friction losses along the pipe—are deduced based on the backward stepwise procedure,
which are quickly implemented in a simple Excel spreadsheet, to rapidly evaluate the relative contribution of each energy
loss component to the amount of total energy losses. An approximate combination formulation is finally proposed to evaluate
total energy drop at the end of the lateral line. For practical purpose, two design figures were also prepared to demonstrate
the variation of total friction losses (due to pipe and emitters) with emitter local losses, and the variation of pipe friction
losses with emitter minor friction losses, versus different emitter spacing ranging from 0.2 to 1.5 m, and various total number
of emitters, regarding two kinds of the integrated in-line emitters. Comprehensive comparison test covering two design applications
for different kinds of integrated in-line and on-line emitters indicated that the present mathematical model is simple, can
be easily adaptable, but sufficiently accurate in all design cases examined, in comparison with the alternative procedures
available in the literature. 相似文献
13.
汶川震区滑坡堆积体坡面侵蚀量测算方法 总被引：1，自引：0，他引：1
在汶川县选取典型滑坡堆积体,采用三维激光扫描仪实地测量滑坡堆积体形态,用图像分析方法鉴别沟道,用于估算堆积体形成后的土壤侵蚀量。根据滑坡堆积体坡面实测点云数据,采用最小二乘法拟合二次曲线,近似为堆积体坡面沟道各横截面发生侵蚀前的坡面线。结合堆积体发生侵蚀后的坡面沟道实测数据,测算各段沟道侵蚀量后估算出滑坡堆积体坡面侵蚀总量。典型滑坡堆积体坡面侵蚀总量为355 m3。采用传统断面法对计算结果进行验证的结果表明,拟合断面法计算的各分段侵蚀沟体积略大于传统断面法计算结果,相对误差为15.6%。5条分段沟道中最大相对误差为27.1%,最小相对误差为7.9%,拟合断面法计算侵蚀沟体积的精度较好。 相似文献
14.
An experimental work leading to the development of economical and improved stilling basin designs for circular pipe outlet
in comparison to Garde's stilling basin [Garde, R.J. & Saraf, P.D., Journal of Irrigation and Power 1986, 145–154], is reported
in this paper. In the present study, attempts are made to develop efficient and shorter stilling basin models keeping the
basin floor at the invert level of the pipe outlet for inflow Froude number Fr = 5.50. The new designs are arrived at by conducting
a systematic experiments on the stilling basin models having appurtenances like a wedge-shaped splitter block, a modified
grid, an intermediate sill and a rounded step. Scour index, a non-dimensional number has been defined to compare the performance
of the stilling basin models using the same erodible material and time of experimental run. The performance of the newly developed
stilling basin models has been compared with that of Garde's stilling basin model G-D∗. The proposed model M is also compared with the earlier stilling basin model M-12, as suggested by Goel & Verma [Journal
of Irrigation and Drainage Systems 15(1), 2001, 81–91]. 相似文献
15.
采用连续方程、动量方程、交错网格和Simplec算法求解,对XP300-3型新型低比转数旋转喷射泵矩形叶轮、转子腔和集流管的内部流动进行了全三维数值模拟.分析了旋喷泵内部流动规律,得到了转子腔及集流管内部流动的速度场、压力场及湍动能的分布规律.设计了5种不同进口形状的集流管,并分别整体组合,比较了该5种模型的优劣,找到了集流管内部流动的一些规律.分析及数值模拟结果表明：集流管椭圆型进口长半轴跟转子腔半径相一致,长短半径相差不大更有利于解决过水断面充分入流的问题,进而减少其水力损失;通过对数据结果进行综合平衡分析和比较,得出了最优的参数组合.研究结果可为旋喷泵的性能预测以及集流管的优化设计和能量损失分析提供理论依据. 相似文献
16.
在新疆635溢洪道整治工程研究的基础上,基于正交设计原理,对溢洪道布置糙条消能工进行6因素3水平的正交试验,试验测得18种组合典型断面的瞬时流速和水深;通过对弯道微元化处理的方法,建立了质量离散系数Cm模型,并结合消能率η对试验结果进行了极差分析;考虑到建立导流效果评价方法的普适性,定义量纲一因子Rd和Rs,对布置参数与工程参数之间的相关性做了进一步分析.结果表明:质量离散系数Cm能够客观地反映糙条消能工的导流效果;就Cm指标影响程度而言,工程参数较布置参数的影响程度占主导地位,在实际工程中,工程参数的确定应充分考虑水流形态;由于Rd和Rs均是量纲一参数,因此在一般整流工程导流效果的评价方法上具有普适性. 相似文献
17.
18.
简要地介绍了当前曲管动力特性的分析方法,采用有限元法实现了管壁与流体的耦合,给出了管道流固耦合的有限元方程,针对90度的曲管,设定了管端入口处的冲击流速,研究了流体速度瞬变过程中曲管的位移特性,在流速变化及流速稳定阶段,分别对两端固支及悬臂曲管模型的管壁节点在不同时刻的坐标轴不同方向的位移进行了比较,判断出曲管节点位移随时间和速度的变化趋势以及位移极值出现的位置,这可为进一步的管道及管路系统的振动噪声研究及设计提供参考。 相似文献
19.
京杭运河底泥起动和冲刷率试验研究 总被引：1，自引：0，他引：1
京杭运河是南水北调东线工程的重要输水通道,减少底泥冲刷引起的污染对保护其水质有重要的作用。利用文献中的底泥起动流速公式和冲刷率公式,推导出起动摩阻流速与湿密度公式、摩阻流速与冲刷率公式。以京杭运河底泥在水槽内进行不同湿密度的起动试验和不同水流条件下的冲刷率试验。试验结果用最小二乘法进行拟合,得到底泥起动时临界起动摩阻流速与湿密度的相关关系,冲刷时摩阻流速与冲刷率的相关关系。结果表明,有关试验数据的相关性较好,对实际工程应用有一定的指导意义。 相似文献
20.
针对螺旋弯管内的流动与传热特性,以螺旋弯管传热试验中试验件模型为研究对象,基于Realizable k-ε湍流模型、第一类热边界条件下的薄壁热阻模型,对不同进口来流条件下,采用Fluent对螺旋弯管内水的流动与换热进行数值模拟.计算得到了螺旋弯管内速度场与温度场的分布,通过数值模拟结果与试验结果的比较,验证了数值模拟方法的正确性.结果表明:随着进口来流雷诺数的增大,螺旋弯管内的二次流迪恩涡核心向弯管管壁扩张;在螺旋弯管小曲率比、来流雷诺数2 280~6 000内,螺旋弯管的强化换热综合性能最佳;对模拟结果数据利用多元线性回归法,推导出螺旋弯管内换热努赛尔数、进出口压力降的准则关系式.研究结果可为螺旋管式换热器设计与优化提供一定的参考依据. 相似文献