Characterising equivalent droplet indicators of sprinkler irrigation from a kinetic energy perspective

Equivalent droplet velocity and diameter are important parameters for measuring the effectiveness of sprinkler spraying; however, non-optical test methods (paper stain, flour pellet, and oil immersion methods) can only obtain the droplet number and diameter. With the widespread use of optical instruments in sprinkler testing, droplet velocity can also be measured, therefore, it has become possible to calculate the average droplet characteristics from an energy perspective. This paper proposes an energy-weighted method for calculating droplet equivalence indicators. Statistical analyses were performed based on five types of sprinkler irrigation droplet distribution data to compare the characteristics and differences between the energy-weighted method and the calculation results of the other methods. The results showed that 1) the velocity outcomes of the energy-weighted droplet equivalent method, empirical formula I, and empirical formula II consistently increase and decrease; 2) the equivalent droplet diameter based on the energy-weighted method is the largest, followed by the equivalent method related to droplet volume, and the smallest is the equivalent method related to droplet quantity; and 3) the equivalent droplet velocity and diameter calculated by the energy-weighted equivalent method can characterise droplets with a high energy contribution. The energy-weighted equivalent droplet velocity and diameter indicators derived in this study provide new ideas for characterising droplet averaging.