Initial Drop Velocity in a Fixed Spray Plate Sprinkler

Abstract

Ballistic simulation has been successfully applied to impact sprinklers. However, ballistic simulation of center pivot sprinkler irrigation has been limited by the difficulty in estimating the initial drop velocity vector in fixed and rotating spray plate sprinklers. Initial velocity is severely affected by the impact of the jet on the sprinkler deflecting plate (or plates). In this work, experimental techniques based on drop photography have been used to obtain the droplet velocity and angle in the vicinity of a fixed spray plate sprinkler by using three different nozzle diameters. Furthermore, simulation techniques based on the inverse solution of drop trajectory were combined to determine the initial velocity vector and energy loss at the spray. Our analysis suggests that the ballistic model can be used to simulate drop inverse trajectory in these sprinklers, although the ballistic model can benefit from 5 to 10% effective drag-force screening. The ratio of initial drop velocity to jet velocity was between 0.67 and 0.82, whereas the kinetic energy losses in the spray sprinklers amounted to 33–55%.