Eulerian–Lagrangian model of the behaviour of droplets produced by an air-assisted sprayer in a citrus orchard

Abstract

During pesticide applications to citrus trees using air-assisted (airblast) sprayers, only a proportion of the volume emitted reaches the vegetation and the rest is lost through drift, evaporation, etc. These losses can be hazardous for the environment. Knowing the characteristics of droplets within the turbulent currents around the canopy could improve the application efficiency. In a previous study, a 2D computational fluid dynamics (CFD) model was used to simulate the effect of a citrus canopy on the airflow from an airassisted sprayer was developed and validated. It considered the first element of the tree canopy as a solid body instead of a porous one. The aim of this study was to analyse the behaviour of the droplets for pesticide applications on citrus by means of an Eulerian-Lagrangian CFD model. It simulated both the air current from the sprayer fan and the wind and the behaviour of the droplets sprayed. Distance, height, velocity, Reynolds number, temperature, geometric and volumetric diameters at different times were obtained. With these parameters, new variables related to the kinetics and evaporation droplets were calculated. Simulation results estimated that 44% of the total sprayed volume reached the target tree, 28% reached adjacent trees, 20% was deposited on the ground and 8% was lost as atmospheric drift. The results largely matched an experimental mass balance carried out under similar conditions. The proposed model appears to be an appropriate tool for simulating treatments with air-assisted sprayers operating in citrus orchards.

Factors affecting aerial spray drift in the Brazilian Cerrado

“…Previous studies reported that smaller droplets have lower weight and therefore are more subject to wind action since the droplet size directly influences the terminal speed [32] [33]. This fact hindered spray deposition, mainly when the aerial spray application uses droplets smaller than 200 μm.…”

Automation and robotics in the cultivation of pome fruit: Where do we stand today?

“…Holterman et al (2017) captured 10 years of data to establish an empirical model for predicting the pesticide spray drift in pome fruit orchards. The model designed by Salcedo et al (2017) focused on the effects of canopy density on the spraying flow and the drift of the product in citrus orchards. This study reported that 28% of the sprayed volume is not deposited on any fruit tree.…”

“…captured 10 years of data to establish an empirical model for predicting the pesticide spray drift in pome fruit orchards. The model designed bySalcedo et al (2017)…”

Average Degree of Coverage and Coverage Unevenness Coefficient as Parameters for Spraying Quality Assessment

“…The model took into account the tree habit and wind flow in the tree crown as well as the speed of the sprayer. On the basis of the model, the amount of liquid carried into the atmosphere (air drift) and into the soil (sedimentation drift) was calculated [21,22].…”