Closed-form solution for the length of drip laterals and easy selection of commercial emitters for low-slope fields under the Hazen–Williams and Blasius resistance equations

This paper proposes a simple method for determining drip lateral length in relatively flat fields in which minor losses are not considered and a uniform emitter flow rate is assumed. This makes it possible to derive a useful relationship in a closed form to determine drip lateral length according to the Hazen–Williams and Blasius resistance equations. An important advantage of the proposed procedure for determining drip lateral length is that it helps users establish the characteristics of the commercial emitters that they should select, an issue that has been poorly addressed in the past. Finally, after deriving this new solution, the same relationship is extended to a case in which minor losses are considered, and the uniform emitters' flow rate assumption is relaxed. The results of all input data sets show that when neglecting minor losses, the relative error between the inlet pressure head estimated with the suggested procedure and that calculated with the exact numerical method is less than 2.5%. However, when minor losses are considered, the number of emitters must not exceed 300 to obtain this threshold error. Several applications are performed, showing the reliability of this new design procedure.