Numerical simulation of the effect of varying dispersion tooth insertion depth on the jet breakup and hydraulic performance

Abstract

Varying the depth that a dispersion tooth is inserted into water jet can cause significant differences in the hydraulic performance of irrigation sprinklers. The effect of insertion depth on jet breakup was investigated by combining the fluid volume method, overset grid technology, and using adaptive grid refinement. Jet fragmentation mode, droplet characteristics, and entropy production were analysed, and effects on sprinkler pattern radius loss, water application rate, and combination uniformity were discussed. Results showed that as water insertion depth increased (from 1.5 to 4.5 mm) the number of ligament produced increased. This was due to enhanced air entrainment, which also increased the number of droplets. However, the relative frequency change in droplets with a diameter up to 400 μm exceeded 20%, whilst that of 400–600 μm diameter droplets remained within 10%. Factors such as high and low velocity transfer, backflow, and air entrainment caused reductions in sprinkler pattern radius with a total entropy production increase of 167.8%. The relationship between total entropy production and radius loss was described using an exponential function with a correlation coefficient of 0.91. When the sprinklers were arranged in a square formation, and the spacing between the sprinklers was equal to the throw radius, an optimal combination of uniformity was achieved by inserting the water dispersion tooth into the central axis of the jet, resulting in a maximum uniformity value of 75.6%. Findings from this study provide a reference for the analysis of sprinkler hydraulic performance.