CFD MODELLING TO TRACK THE PATH OF PESTICIDE DROPLETS FROM AN AIR-ASSISTED ORCHARD SPRAYER

Abstract

To predict the fate of pesticide droplets generated by an air-assisted orchard sprayer, a CFD model was developed. The modelling was based on a Lagrangian multiphase flow model. The effects of fan rotational and sprayer ground speeds on the droplet distribution were studied. The simulation was done for fan speeds of 1360 and 1836 rev/min, and tractor speeds of 1.67 and 2.58 m/s. To consider the speed of the tractor a moving coordinate system was implemented. At the exit of the fan, the vertical velocity profile of the air jet was measured and used as an inlet boundary condition for the model. The droplets were injected from eight 80° hollow cone nozzles with a 5 bar pressure. The distribution of the sprayed droplets was highly influenced by fan rotational and sprayer ground speeds. With an increase in sprayer ground speed, there was an increase in the deflection of droplets opposite to the driving direction. The distance the droplets travelled to the direction of the jet was increasing with an increase in fan speed, but it was decreased with an increase in tractor ground speed. There was a good agreement between the predicted and measured vertical droplet distributions. Canopy interaction was not considered at this stage.