Water distribution model for center pivot end gun sprinklers

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%.

Influence of Canopy Interception of Soybean and Corn on Water Distribution of Center Pivot Sprinkling Machine

“…The existing studies on sprinkling machines focus on the hydraulic performance [5][6][7][8], failing to explore deep into the relationship between sprinkler irrigation and canopy interception. Similar to natural rainfall, the sprinkled water can be intercepted by crops.…”

Asymmetric Wetted Sector Angle in Water Distribution of Traveling Gun Irrigation Systems

“…Asymmetric adjustment of the sprinkler wetted angle has been recommended for center pivot end-guns (Prado et al, 2019); this procedure leads to the application of a larger amount of water to one side of the irrigation lane (Figure 3). Increasing this asymmetry (β = 90º) causes a stark reduction in the wetted transverse extension of the gun sprinkler and a rise in applied depth for the wetted sector angles between 180 and 270º.…”

“…On digital simulations a gun sprinkler moving along the lane (Figure 1) with a constant linear speed of 50 m h -1 , a flow rate of 50 m 3 h -1 , and a radius of throw of 42 m was considered. As pointed out by Prado et al (2019), the geometric shape of water distribution curves from gun sprinklers, working with a suitable combination of nozzle diameter and pressure, tends to a uniform radial profile. Hence, the water application rate caught in a grid of collectors, as a function of the radial distance of a gun sprinkler with uniform theoretical radial profile, can be computed by: 5In which: i(r)water application rate as a function of the radial distance (r) from the sprinkler, mm h -1 ; rradial distance from the sprinkler, m; Qsprinkler discharge, m 3 h -1 ; Rradius of throw in a no-wind condition, m, and sprinkler wetted angle, deg.…”