Pressure distribution on center pivot lateral lines: analytical models compared to EPANET 2.0

Abstract

The analysis of friction head-loss spatial distribution along center pivot lateral lines represents an important step when evaluating energy-use efficiency of center pivot irrigation systems. This work compares head-loss spatial distribution along center pivot lateral lines computed with the hydraulic simulator EPANET 2.0 with head-loss spatial distribution predicted by four different analytical models. For the different center pivot lateral line configurations considered in this study, two different sets of friction head-loss values were analyzed. These two sets represent head-loss estimates obtained with different values of the flow rate exponent (α) in two main friction head-loss equations: Darcy–Weisbach (α=2) and Hazen–Williams (α=1.852). On both sets, the four analytical solutions assessed in the current work estimated head-loss values similar to those computed by the hydraulic simulator EPANET 2.0. These results show that the detailed description of flow rate distribution along the center pivot lateral line required by the numerical method did not improve the accuracy of the calculated head-loss distribution. On the data set of values produced by using the Hazen–Williams head-loss equation, the analytical solution associated with the most complex mathematical expression provided the lowest deviation in relation to head-loss values computed by EPANET 2.0. On the data set of values produced by using the Darcy–Weisbach head-loss equation, assuming a fully turbulent flow regime, the four analytical models presented the same deviation in relation to the values computed by EPANET 2.0.