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1.
A computer model, SPRINKMOD, was tested with field data collected from a simple sprinkler irrigation system in operation.
The original data for laterals and the amount and way leakage is considered were modified to evaluate the model sensitivity.
The model predicted the pump station flow rate within 2% and the pump station pressure head within 5% with the original data
collected. For this irrigation system, no practical effect was observed in the system operating point by changing the lateral
pipe characteristics, lateral leakage amount and distribution, lateral pipe roughness and lateral local loss coefficient for
flow past a riser outlet. The amount of leakage had more effect on the model simulation of pressure heads than the way leakage
was considered, localized or distributed along the laterals. The use of a variable local loss coefficient, K
r, along the 350-m hand-move laterals had a negligible effect on both system operating point and distribution of pressure heads
along the laterals.
Received: 14 February 1998 相似文献
2.
Numan Mizyed 《Irrigation and Drainage Systems》2002,16(1):53-68
A model to solve the hydraulics of trickleirrigation units is developed in thisstudy. This model is based on utilizingNewton Raphson technique. The modelconverts laterals into equivalent outletsthrough utilizing a simple power relationbetween inlet lateral discharge andhydraulic head. This relation is obtainedthrough least squares analysis betweeninlet lateral discharge and hydraulic head. This study showed that this relation withonly two coefficients is sufficient todescribe the relation between inlet lateraldischarge and hydraulic head. Based onthis relation, the model converts manifoldlines into equivalent laterals and solvestheir hydraulics by Newton Raphsontechnique. After that solution, the modelevaluates trickle irrigation units byestimating statistical uniformity andChristiansen uniformity coefficients andchecks the solution obtained throughforward step method for each lateral. Several numerical examples for utilizingthe model are presented in this paper.Palestine Authority 相似文献
3.
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
4.
A method for designing microirrigation laterals on nonuniform slopes was developed using the finite element method. Six representative
nonuniform slope patterns were discussed in detail. The design principle was implemented based on the results of computer
simulations. It was found that a single lateral is suitable for Pattern I while paired laterals are better for Patterns II
∼ VI in most cases. The diameter of a single lateral or paired laterals may have two solutions for a required uniformity of
water application and the length may have multiple solutions. When the required average emitter discharge, required uniformity
of water application, and one parameter (either length or diameter) of a single lateral or paired laterals are given, the
unknown parameter, best submain position (paired laterals) and operating pressure head can be accurately designed using personal
computers. The design procedures are described.
Received: 2 November 1995 相似文献
5.
6.
滴头锯齿型迷宫流道消能特性的流体动力学分析 总被引：3，自引：0，他引：3
在对所选取的3种代表性锯齿型迷宫式滴头流道参数进行精确测定的基础上,利用圆管紊流理论和CFD流场模拟软件对锯齿形迷宫流道的消能机理进行了研究。结果表明：光滑圆管紊流理论不足以解释锯齿型迷宫流道的消能机理;压力沿流道长度方向呈线性递减,各消能尖角单元压力损失相等,符合线性叠加规律;摩阻系数随着压力增加而降低,并很快稳定在一定数值上;在中、高压区滴头流道内部流动为紊流,在低压区可能存在从层流到紊流或者光滑紊流到全紊流的流态转捩行为。 相似文献
7.
为了提高滴灌系统水力设计的准确性,基于有限元原理,提出一种计算薄壁内镶贴片式滴灌带能量损失和灌水均匀度的方法,局部水头损失根据贴片式滴头结构、管内压力和管道壁厚确定,沿程水头损失通过改进Darcy－Weisbach公式编写计算机程序,分析了不同滴灌带的水头损失及均匀度变化规律,并与《微灌工程技术规范》中推荐计算方法的结... 相似文献
8.
Antonio Pires de Camargo Bruno Molle Séverine Tomas José Antônio Frizzone 《Irrigation Science》2014,32(3):181-191
Ageing of drip irrigation systems due to clogging of emitters is considered the largest maintenance problem in microirrigation and this problem is enhanced in subsurface irrigation systems. Whatever the source of the clogging problem, a methodology for early detection of clogging in the field can be useful in decision-making about deploying cleaning processes (flushing or injection of chemicals) and avoiding replacement of laterals. This work presents a methodology for simulating clogging conditions able to reproduce the effects of clogging on pressure profiles, head loss, and emitters flow rate distribution along a single levelled lateral with constant inlet pressure. This methodology was validated by several experiments conducted under controlled conditions of clogging induced by changes in the flow rate of emitters. The effects of clogging intensity and position on hydraulic parameters of a single lateral were analysed in detail and aspects relating to pressure, head loss, and flow rate measurements were discussed. For a given lateral set-up, it is possible to draw a chart relating flow rate and head loss for various levels and positions of clogging. Assuming that measurements of head loss and flow rate are available, this diagram enables immediate estimation of the level and location of clogging, which is useful for deploying maintenance routines. Finally, a protocol was proposed to detect the level of clogging and estimate its position along a levelled lateral under constant inlet pressure. Although constant lateral inlet pressure is atypical in large agricultural settings, it may occur in greenhouse or experimental settings. 相似文献
9.
An improved method for designing microirrigation submain units 总被引：1，自引：0，他引：1
A method was developed for designing microirrigation submain units using the lateral flow rate equation, finite element method,
and golden section search. Characteristics of water application uniformity affected by lateral parameters (length and diameter)
and submain parameters (length and diameter) were analyzed using computer simulations. The design principle was then implemented
based on the simulation results. When the required average emitter discharge, the required water application uniformity, one
lateral parameter (length or diameter), and one submain parameter (length or diameter) are given, the optimal values of another
lateral parameter, another submain parameter, best submain position (paired laterals), and operating pressure head can be
accurately designed using a personal computer. A submain unit designed using this method has a minimal initial cost. This
method is suitable for both submain units with uniform lateral lengths (in regular fields) and nonuniform lateral lengths
(in irregular fields).
Received: 28 May 1996 相似文献
10.
Design of microirrigation laterals at minimum cost 总被引：1，自引：0，他引：1
Based on the design methods of finite elements and golden-section searches, a method was developed for designing microirrigation
laterals at minimum cost. Characteristics of water application uniformity as affected by lateral diameters and lengths were
analyzed. When the required average emitter discharge is known, the relationships of water application uniformity, best submain
position (paired laterals), and operating pressure head as a function of the lateral diameter and length can be accurately
determined using a personal computer. The lateral diameter and length can then be determined from a contour map representing
water application uniformity as a function of the lateral diameter and length (computer calculation). The best submain position
and operating pressure head for this lateral diameter and length is then determined by computer calculation. This method is
suitable for designing microirrigation laterals on both uniformly and nonuniformly sloping fields.
Received: 30 May 1997 相似文献
11.
多喷头支管设计的常规方法是采用克里斯琴(Christiensen)导出的等流量、等出流间距、等管径的多孔系数法,但实际喷灌工程中,各喷头流量并不相等,间距也可能不同。针对这个问题,本文通过建立支管模型,提出了支管内各管段通用的水力计算方程式,可求解出精确的支管流量和水头。本方法用于多种管径,出流间距可不相等的管段组成的喷灌支管设计。 相似文献
12.
A simple procedure was developed for the design of low-cost, gravity-fed, drip irrigation single-manifold subunits in hilly
areas with laterals to one or both sides of the manifold. The allowable pressure head variation in the manifold and laterals
is calculated individually for different pressure zones, and the manifold subunit design is divided into independent processes
for laterals and manifold. In the manifold design, a two-stage optimal design method is used. In the first design stage, the
pipe cost is minimized and a set of optimal manifold pipe diameters is obtained. In the second design stage, a partial list
of available diameters is prepared based on the calculated optimal diameters, and the lengths for available diameters and
pressure head of every lateral location along the manifold are calculated. The size of each of the pressure sections is determined
according to the pressure head distribution along the manifold. Using the proposed methodology, the minimum manifold pipe
cost is obtained, and the target emission uniformity is satisfied for gravity-fed drip irrigation subunits. 相似文献
13.
当离心泵扬程略低于实际需求时,可以通过修锉叶片出口提高其水力性能.文中对单级单吸离心泵叶轮进行修锉,对比修锉前后试验发现,扬程、效率分别提高了9.8%和6.7%.同时采用CFX软件对该泵在设计工况下的全流场进行了非定常数值计算,对比分析了修锉前后内流场的变化.基于ANSYS Workbench平台,对叶轮进行单向流固耦合计算,分析了修锉叶片出口对叶轮强度的影响.结果表明:叶片出口修锉后,出口尾迹区的绝对速度增大且相对速度减小,导致扬程上升;修锉后叶片出口边的逆压力梯度明显减小,阻止了边界层的分离,减少了摩擦和分离损失,从而提高了效率;叶轮最大等效应力与修锉前相比,其差别随着相位的不同而不同;各相位下,修锉后的叶轮最大总变形均大于修锉前.研究结果为改善离心泵内流场提供了一种可靠的方法. 相似文献
14.
A study was conducted at the department of Agricultural Structure and Irrigation, Harran University, Sanliurfa, Turkey, to
determine the effect of increased irrigation water temperature at various irrigation system pressures on emitter flow rate,
lateral elongation, and Standard Flow Rate Index for six different brands of drip laterals. Test materials consisted of seven
pressure and seven non-pressure compensating irrigation laterals from different manufacturers. Tests results showed that (a)
tensile resistance stress tests indicated that 25% elongation levels were reached at about 40 kg of load. On average, pressure
compensating laterals reached 25% elongation at 38 kg, while non-pressure compensating laterals reached 25% elongation at
32-kg load. There was no clear indication of the tested brands’ lateral wall thickness on the measurement, (b) pressure-regulated
drip emitters had no or limited flow rate change due to increased irrigation water temperature, whereas non-pressure compensating
emitters had significantly (P < 0.05) increased flow rates, and (c) finally, increased irrigation water temperature resulted in decreased flow rate variations
that had a positive effect on standard deviation. Standard uniformity values improved with decreased flow rate variations
in drip emitter flow rates. 相似文献
15.
A computer model was developed to simulate pressure and flow rate distribution along pipes and laterals of pressurized irrigation
systems in operation. The software runs in a Windows environment and is capable of simulating irrigation systems having multiple
pump stations combined in series and/or in parallel, booster pump stations, parallel pipes and looping pipes. Hand-move, wheel
line and center pivot laterals with pressure regulators, one or two drop pipes per outlet and booster pump can be simulated.
Leakage can be included in the main pipe network or along the laterals. Lateral inlet pressure can be set to an upper limit
to simulate valve closure. Practically any type of nozzle and pump can be simulated since cubic spline functions are used
to interpolate values from head-flow rate sets of data. To accomplish these capabilities, algorithms were developed and adapted
to convert laterals into a set of head-flow rate data so that a simplified algorithm could be adapted to solve the entire
pipe network. A user-friendly interface was designed to allow data for pumps, nozzle and pressure regulators to be interactively
entered, edited and analyzed prior to the simulation run. The layout of the irrigation system can be drawn on screen using
the mouse. Data can be independently entered and edited for each irrigation system component already drawn in the screen,
at any time and in any order. Data for the entire irrigation system are verified at many levels before the simulation is run,
to make the model less susceptible to crash. The model proved to be a practical tool for upgrading and designing pressurized
irrigation systems.
Received: 20 November 1997 相似文献
16.
基于二分法的微灌毛管水力设计 总被引：2，自引：0，他引：2
根据微灌毛管水力学特性,采用二分法搜索原理,并与逆递推法相结合,提出微灌毛管水力解析与设计方法。利用计算机编程从毛管末端向毛管进口逆序递推,可以快速、方便地求解出毛管各个孔口的压力和流量,设计毛管运行的水力参数,校核平均流量、流量偏差率等设计控制指标。实例验证结果表明,该设计方法具有直观、简便和快捷的特点,易为非专业人员理解与应用,具有较高的求解效率和计算精度。 相似文献
17.
Dimensional analysis approach to estimate local head losses in microirrigation connectors 总被引：1，自引：0，他引：1
Danieli Bariviera Zitterell Jose Antonio Frizzone Osvaldo Rettore Neto 《Irrigation Science》2014,32(3):169-179
Local losses, which affect the uniformity of water application, are often ignored in the design of irrigation systems. Some accessories have no simple, efficient equations to estimate these losses. The main objective of this work was to develop an equation to estimate the local head loss in lateral passage connectors. Fifteen connector/pipe combinations were tested. The connectors were characterized by their internal diameters and dimensions. The local head loss was determined by subtracting the head loss on the connector and pipe from the head loss on the pipe. The parameters affecting the local head loss were defined as dimensionless terms using Buckingham’s theorem. A mathematical model was developed that presented a determination coefficient of 93.31 %. Elements such as the inner diameter of the connector, pipe length, connector, water flow velocity, Reynolds number and Froude number influenced the local head loss in the connectors. The model was compared with the observed data and presented excellent performance. It can be used to calculate the local head loss in lateral passage connectors. 相似文献
18.
19.
机压喷灌干管管网优化 总被引：2，自引：0，他引：2
在考虑了机压管道式喷灌系统配水干管流量变化的基础上，提出了这一系统干管管网优化的线性规划模型及计算方法。应用这一方法，可在保证各支管入口处所需流量和压力的条件下，确定水泵扬程及干管尺寸最优值，以使干管管网系统年费用值达最小 相似文献
20.
对管道中非定常流动进行了研究,导出了流体在管道中流动时,实用的特征线法的计算方法和公式。该方法是从Ｎａｖｉｅｒ－Ｓｔｏｋｅｓ方程和连续性方程出发,结合流体实际流态状况及摩擦损失函数等,将难以求解的流体偏微分方程组转换为便于工程数值计算的等价差方程组,从而解决了液压管道中液体非定常流动的计算问题,它能很好地满足实际工程计算需要,是研究液压系统动态问题的一种有效方法。 相似文献