Computational fluid dynamics modelling of orchard sprayer performance: Machine type and operational parameters characterization.

The relative balance between environmental contamination and biological efficacy determines the performance of agricultural sprayers. This balance is mainly affected by the design and operational parameters of the sprayers apart from the tree architecture and environmental conditions. The design and operational parameters of the sprayer have been analysed in this study to address this issue. The performance of three orchard sprayers (BAB Duoprop, Hardi Condor V and Hardi Tango) were characterized to see the effect of machine design on on target and off target deposition. Fan speed and deflector setting were the two operational parameters considered for this study. This analysis was done using Computational Fluid Dynamics (CFD) . Albuz ATR orange and red nozzles, respectively, for the first two and for the last sprayer were used for spray flow. The CFD models represent controlled indoor trials carried out using artificial pear trees. The three different sprayer designs gave different air and spray flow profiles. The CondorV and Tango sprayers gave a relatively higher velocity air passing the canopy near the ground and there is a higher spray coverage at higher heights for the Duoprop and Tango sprayers than for the Condor V sprayer. In terms of the two operational parameters, shifting from low to high gear setting increased both the on target(leaf and trunk) and off target deposition due to the increase in the penetration capacity of the spray. Shifting the deflector setting from optimal to extreme setting also increased both the on and off target depositions. But the increase in trunk and leaf deposition obtained by changing the deflector setting from optimal to extreme is minimal compared to the resulting drift problem.