Simulation of Drift of Discrete Sizes of Water Droplets from Field Sprayers

Abstract

The drift distances of water droplets from field sprayers were determined for several variables with a computational fluid dynamics computer program. The simulation variables for drift distances up to 200 m included: droplet size (10 to 2000 mm), wind velocity (0.5 to 10.0 m/s), initial droplet velocity (0 to 50 m/s), discharge height (0.25 to 4.0 m), temperature (10 to 30 C), relative humidity (10 to 100%), and 20% turbulence intensity. Except at low temperature and high relative humidity, all 50-mm-diameter and smaller droplets completely evaporated before depositing 0.5 m below the point of discharge for all simulated conditions. Drift distances increased with increasing wind velocity and discharge height, but decreased with increasing initial downward droplet velocity for 100-mm-diameter and larger water droplets. Changes in ambient temperature and relative humidity had much greater influence on drift distances of water droplets less than 100-mm-diameter than on 200-mm-diameter and larger droplets.