CONTRIBUTIONS TO THE STUDY OF SPRAYING OPERATIONS IN THE CONTEXT OF SUSTAINABLE AGRICULTURE
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The global agriculture sector faces many challenges in its mission to meet the growing demand for food and fiber. Climate change, increasing population growth, emergence of crop diseases, damages to crops from rodents and critters, and shrinking farming land in some regions are among these challenges. The application of agrochemicals has proven to be an efficient answer to some of these challenges. Through three themes, this thesis investigates how spraying configuration can contribute to the reduction of spray losses in the context of sustainable agriculture. The first theme introduces a method for fluid quantification from a sprayer jet using a Particle Image Velocimetry (PIV) system in combination with imaging processing. Experimental results revealed that fluid flow measurement through PIV is reliable and PIV can be used to predict the spray pattern accurately and reveal velocity distribution. The second theme investigates the velocity distribution of an extended flat fan nozzle to determine the weak jet areas, which have high risks of droplet drift, using the Particle Image Velocimetry (PIV) method and Computational Fluid Dynamics (CFD) with volume of fluid (VOF) simulation approach. Particles in the central region of the spray sheet have maximum kinetic energy and have the ability to hit the right target on the plant surface, while liquid particles in the surroundings of this central area have less velocity with minimum kinetic energy and have maximum chances to be off-target during spraying. The third theme deals with the development of a mathematical model to jointly minimize spraying time and drift losses. The obtained bi-objective model is solved for a case study published in the crop protection literature. The results show that valid and reasonable solutions can be obtained by selecting the appropriate combination of boom height, nozzle spacing, nozzle type and tractor travel speed.