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Simplified Approach for DesigningLength of Microirrigation Laterals

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Applied Engineering in Agriculture. 33(1): 75-82. (doi: 10.13031/aea.11882) @2017
Authors:   Xueliang Ju, Pute Wu, Paul R. Weckler, Delan Zhu
Keywords:   Analytical approach, Length, Microirrigation, Paired laterals.

Abstract. A simple, direct, and easily adaptable analytical approach was developed for determining the length of the drip laterals laid on uniformly sloping grounds. The emitter flow variation was used as the index of water application uniformity. A dimensionless length design parameter was developed by reformulating the analytical expressions of emitter flow variation of the single inlet lateral and paired laterals. The length design parameter was defined as an implicit function of the pressure loss ratio. The relationship between length design parameter and pressure loss ratio was expressed by the graphs and regression equations. The condition for designing the length of the paired laterals was the length design parameter lying between ≥0 and ≤2.801. In most situations, there will be only one solution of design length of the lateral. When length design parameter is 2.801, there will be numerous solutions of length for both of the single inlet lateral and paired laterals. Based on the ranges of the length design parameter, the design equations of the length of the single inlet lateral and paired laterals were derived with the pressure loss ratio as the design variable. The analytical expressions of inlet working pressure head of microirrigation laterals were also simplified based on the energy gradient line method. When the emitter design flow, emitter flow variation criterion, and lateral diameter were provided, the length and inlet working pressure head of the microirrigation laterals could be easily calculated without performing complex computer operations or tedious computations. A comparison test with two numerical design cases covering various conditions indicated that the proposed approach could produce accurate results as those of the previous methods for practical purposes. By using the developed analytical expressions and regression relationships, the proposed approach provided a more simplified and adaptable design procedure than the traditional methods.

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