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A simplified method for the resolution of lateral hydraulic problems in laminar and turbulent flow is presented. In the first stage, the head losses are calculated by applying the Darcy--Weisbach equation with a discrete and constant outflow model, which leads to a correction parameter equivalent to Anwar's [G.sub.a] factor. The difficulty that arises from variation of the friction factor along the lateral (due to discharge flow) is overcome by means of an equivalent friction factor ([f.sub.eqN]). In the second stage, this head loss model is used together with a variable discharge model based on Taylor polynomials to make a better estimate of the flow rate distribution by means of a successive-approximations scheme. This new approach directly allows the computation of the real mean lateral's outflow and the minimum and maximum discharges. In the third stage, the previous results can be improved (if desired) by taking into account the nonconstant outflow distribution model developed in the previous stage. The method proposed is useful to work out the hydraulic computation of laterals with the inlet segment at full or fractional outlet spacing, and complex laterals when a different pipeline diameter, slope, flow regime, or emitter gap has to be considered. The results are comparable to those obtained in the literature. DOI: 10.1061/(ASCE)0733-9437(2002)128:5(278) CE Database keywords: Sprinkler irrigation; Trickle irrigation; Design; Computation; Laterals.

A new approach for solving lateral hydraulic problems in laminar or turbulent flow is presented. The outflow is treated as a discrete variable event by means of Taylor polynomials used to calculate flow rates along the lateral (minimal outflow included). The friction head losses are calculated using the Darcy-Weisbach equation with a nonconstant logarithmic friction factor f. This algorithm allows hydraulic computation for a set of connected laterals (with different pipeline diameter, slope, flow regime, or emitter spacing) if a residual outflow [Q.sub.r] is used. The new approach can be used to calculate flow variation on laterals and submains in trickle or sprinkler irrigation systems without an excessive calculation effort. Results are comparable to those obtained in the literature.

Discusses the article "Equivalent Friction Factor Method for Hydraulic Calculation in Irrigation Laterals," by Pedro Vallesquino and Pedro L. Luque-Escamilla, published in the September/October 2002 issue of the "Journal of Irrigation and Drainage Engineering." Total head losses for different inlet segments; Comparison of characteristic parameters computed from two alternative equation sets; Computation of head losses using energy gradient line.