An assessment of hydraulic design of trickle laterals considering effect of minor losses

Abstract

The accurate design of trickle irrigation laterals needs to determine the total energy losses that includes the pipe friction losses along the lateral line and the local pressure losses, sometimes called minor losses, due to the protrusion of emitter barbs into the flow. Evaluation of energy losses is usually carried out by assuming the hypothesis that minor losses can be neglected, even if 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 installed along the lateral line. In this study, a simple analytical procedure is presented to evaluate the effect of minor losses which is characterized by a coefficient αi, expressing the amount of minor head losses as a fraction of the kinetic head, on trickle lateral design. According to both the design cases of without and including minor losses, the dimensionless design curves were developed for both the various lateral diameters and lengths. The results of two practical examples for designing either the diameter or the length indicated that, in some design cases, neglecting minor losses may lead to erroneous designs of the lateral diameter and length. This method is simple and easily adaptable to solve lateral hydraulic problems but sufficiently precise in comparison with the alternative procedures. The proposed equations are useful when applied for design and evaluation purposes and offer a practical field solution for laterals used in irrigation systems.

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