Water distribution model for center pivot end gun sprinklers

Modelo de distribuição de água para canhões finais em pivô central

ABSTRACT

End gun sprinklers can increase the irrigated area by center pivot irrigation systems without a substantial investment. This study was carried out at the Universidade Federal de Lavras, MG state, Brazil, and aimed to describe and validate a water distribution model for center pivot end gun sprinklers. The gun sprinkler PLONA-RL250®, attached at the end point of a center pivot, was used to evaluate the model in field tests. The sprinkler working conditions considered were nozzle diameters of 14 x 6 mm, working pressure of 292 kPa, and four asymmetric wetted angle adjustments (95 + 20º; 90 + 90º; 60 + 60º; 45 + 45º). These tests were carried out for wind speed lower than 0.9 m s^-1. The measured and simulated irrigation depths showed an average absolute difference of 0.65 mm and determination coefficients from 71.55 to 89.37%. Based on the confidence coefficient (c = 0.82) the model can be classified as very good (0.76 ≤ c ≤ 0.85). Sprinkler wetted angle adjustment of 110º (95 + 20º) resulted in uniform water distribution and, for effective radius of throw between 70 to 90% of the gun sprinkler´s radius of throw, this working condition resulted in Christiansen’s uniformity greater than 80%.

Key words:
nozzle diameter; wetted angle; working pressure