A model for predicting effects of rotation variation on water distribution of rotary sprinkler

This study proposes a three-dimensional spray calculation model for a rotary sprinkler to evaluate the characteristics of water droplets under different rotation speeds. The water droplet trajectories are calculated using ballistic trajectory equations, and the secondary breakup of droplets is computed based on the WAVE breakup model. A water superposition model is proposed to calculate the water application rate within the spraying wetted area, and the accuracy of the model is verified through experiments at a rotation speed of 2 rpm. The characteristics of the sprayed droplets are analyzed and compared for five different rotation speeds. The results show that the relationship between droplet velocity and diameter follows an exponential function, while the droplet diameter and distance from the sprinkler follow a logarithmic function. As the rotation speed increases, the diameter of droplets decreases, the velocity and the peak value of specific power increase, and the area of the radially wet region expands. At the pressures of 200 and 300 kPa, the model has average standard deviations of 0.46 and 0.35, respectively, for predicting the water application rate. The prediction errors of the irrigation peak are 8.69