Iterative calculation of local head loss coefficient of emitters in lateral lines

Abstract

This study aimed to iteratively set the local head loss coefficient of the Naan® micro-sprinkler, model 7110 Hadar, installed in a lateral irrigation line. To evaluate the total head loss along the lateral line, tests were performed using a rigid PVC pipe with an inner diameter of 15.8 mm, 12 m in length, and 24 micro-sprinklers inserted along the pipe, regularly spaced 0.5 m. In the tests carried out for four micro-sprinkler nozzle diameters (0.9, 1.0, 1.1, and 1.2 mm) and six inlet pressure head values (5, 10, 15, 20, 25, and 30 m) in the line, the pressure head difference between inlet and outlet in the pipe and the discharge of each emitter along the pipe were measured. The head loss computation was performed by the step-by-step procedure, starting from the downstream end to the upstream end of the line; since varying the local head loss coefficient values iteratively, the total head loss measured in the tests was equal to the calculated. For the different working conditions of the inlet pressure head and the micro-sprinkler nozzle diameter, the local head loss coefficient had values from 0.051 to 0.169. Relating the discharge values measured and estimated along the lateral line, the confidence coefficient of 0.9991 was verified, and the calculation procedure was considered optimal.

Performance assessment of the TORO Company Neptune PC AS dripline

“…Regarding the relationship between the total flow rate in the dripline and the local head losses due to the single 90° curve or to the single Tee (Figure 3), the behavior is clearly not linear, confirming, as expected, the theoretical results of the Darcy-Weisbach equation, where a parabolic behavior between local head loss and mean water velocity in the pipe (and hence flow rate in the pipe) is reported (e.g. Prado et al, 2021). The results depicted in Figure 3 can help in adequately assessing the local head losses that can occur using the selected dripline and special connections.…”