A good hydraulic design of drip irrigation systems requires an accurate evaluation of the friction head loss that occurs in pipes as well as the local head loss induced by the presence of emitters. Previous approaches on theoretical design usually neglect the local emitter head loss or consider it equal to the friction loss produced by an equivalent length of the straight pipe, which may lead to substantial errors. In this study, an improved finite element-based formulation is presented for the hydraulic analysis of drip irrigation subunits. Local head loss is calculated as a fraction of the kinetic head using the results from recent experimental studies on on-line and integrated in-line emitters (Method 1), or by the equivalent length (Method 2). A custom Matlab software script was developed and the two methods are compared for accuracy and convergence speed. For practical purposes, the head loss components along lateral direction are analyzed for two types of in-line emitters and a manifold design example is also provided. Acquired data indicate that considering an equivalent length as a constant value leads to a higher percent error between the numerical solution and the experimental data. The percentage of local head loss to the total head loss varies dramatically from 6.3 to 49.2% and this result is in good agreement with the results from alternative procedures available in the literature. The decrease in the local head loss coefficient allows a slight increase in manifold length. In general, the finite element model with solution method 1 can be a fast, accurate, and convenient way of designing a drip irrigation pipe network system.

中文翻译：

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考虑局部滴头水头损失的滴灌子单元水力分析的改进有限元模型

良好的滴灌系统水力设计需要准确评估管道中发生的摩擦水头损失以及由于滴灌器的存在引起的局部水头损失。以前的理论设计方法通常忽略局部发射器水头损失或认为它等于等效长度直管产生的摩擦损失，这可能会导致大量误差。在这项研究中，提出了一种改进的基于有限元的公式，用于滴灌子单元的水力分析。局部水头损失计算为动能水头的一部分，使用最近的在线和集成在线发射器的实验研究结果（方法 1），或等效长度（方法 2）。开发了一个定制的 Matlab 软件脚本，并比较了两种方法的准确性和收敛速度。出于实用目的，分析了两种类型的直列式发射器沿横向的水头损失分量，并提供了一个歧管设计示例。获得的数据表明，将等效长度视为常数值会导致数值解与实验数据之间的误差百分比更高。局部水头损失占总水头损失的百分比从 6.3% 到 49.2% 变化很大，这个结果与文献中可用的替代程序的结果非常一致。局部水头损失系数的降低允许歧管长度略有增加。一般来说，求解方法 1 的有限元模型可以快速、准确、