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RESUMO:Neste trabalho apresenta-se um estudo numérico-experimental do comportamento da agitação de fluido em reservatórios de pulverizadores agrícolas. Uma adequada agitação da calda de defensivos agrícolas em um reservatório é muito importante para garantir a ho mogeneidade da pulverização ao longo de toda a cultura. O objetivo do estudo foi avaliar a viabilidade da utilização de um modelo computacional aplicado ao problema de agitação de calda em reservatórios de pulverizadores agrícolas, e assim, auxiliar no projeto dos mesmos, com economia de tempo e custo. Deste modo, resultados de simulações computacionais de fluidodinâmica (CFD) foram comparados a testes experimentais normalizados. Utilizando um modelo monofásico (água), avaliaram-se os perfis de velocidades e de tensões de cisalhamento na parede do reservatório, a fim de possibilitar a visualização do comportamento do fluido em agitação e relacionar essas variáveis com a concentração de resíduos. A comparação entre resultados experimentais e o modelo computac ional desenvolvido mostrou-se viável, indicando que regiões com baixos valores numéricos de tensão de cisalhamento estavam em concordância com as regiões de alta deposição de cobre da solução-teste. PALAVRAS-CHAVE:agitação em reservatórios, pulverização agrícola, fluidodinâmica computacional. NUMERICAL AND EXPERIMENTAL ANALYSIS OF PESTICIDE SPRAY MIXING IN SPRAYER TANKSABSTRACT: This paper presents a numerical and experimental study of spray fluid performance with stirring in tanks of agricultural sprayers. The pesticide spray should be stirred properly to ensure spraying homogeneity throughout the entire crop. The aim of this study was to evaluate the feasibility of using computer models in pesticide spray stirring and, thus, reducing operational time and costs. Therefore, results of computer simulations of fluid dynamics (CFD) were compared to standard experimental tests. We evaluated shear stress and speed profiles against tank wall using a monophasic model (water). Thus, we could verify the fluid performance during stirring, and relate these variables with residue concentrations. The comparison between experimental and computational model was feasible since areas with lower numerical values of shear stress were in line with areas with high copper deposition.KEYWORDS: tank stirring, farm spraying, computational fluid dynamics. INTRODUÇÃOA eficiência da homogeneização das caldas de defensivos agrícolas ao longo do reservatório de um pulverizador tem grande impacto na qualidade da aplicação e no tratamento de uma cultura. Os solventes utilizados, normalmente água, são substâncias usadas para reduzir a concentração do princípio ativo na formulação. Podem ajudar na ação mecânica do produto, mas não influir diretamente em sua toxidez, sendo, portanto, inertes ao agente de dano. A subdosagem ou superdosagem de um determinado agroquímico no tratamento de uma cultura pode causar-lhe danos, tornando muito importante a homogeneização dessa solução.

This study presents a numerical and experimental comparison of two different types of radial fans used in an agricultural fertilizer spreader at a rotation of 4000 rpm. The numerical analysis was validated through experiments conducted on a test bench using a hot-wire anemometer for velocity measurements and a Pitot tube for pressure readings. A simulation of the agricultural fertilizer spreader was carried out after the experimental validation of the mathematical models of the radial fans on the test bench to evaluate the air distribution behavior along the application nozzles, which was compared to the experimental results. A turbulent mean-field was obtained using the Reynolds Averaged Navier Stokes (RANS) and the k-Epsilon turbulence model was used for two equations. The computational fluid dynamics software CFX 18.1 was used to solve the transport equations. Unstructured tetrahedral meshes generated by the ICEM CFD 18.1 software were used in all models. The applied method is adequate and able to reproduce the fluid-dynamic behavior of airflow in pneumatic systems of agricultural fertilizer spreaders, avoiding the need for prototypes.

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The sloshing phenomenon occurs in partially filled tankers due to sudden movement can affect the tank structure integrity and impair the dynamic stability of the tanker. The effects of sloshing phenomena in a spray mixture tank due to acceleration or deceleration of the agricultural vehicle is investigated under three filling levels of 25%, 50%, and 75%. The pressure time distributions on the tank wall were evaluated by using a multiphase transient model (water and air as an ideal gas) and a free surface flow in a homogeneous model. It was possible to verify the wave behavior of sloshing. The condition of 75% tank filling volume generated the highest pressure on the tank wall. The effectiveness of two types of vertical baffles in suppressing pressure was numerically investigated. Shear stress on the tank bottom wall under these proposed arrangements was analyzed by steady-state models and mechanical agitation, considering a filled tank. The proposed solution based on two partial vertical baffles and a central gap was the most effective. It promotes the higher reduction of wall impact pressure and other sloshing instabilities and maintains similar results of mixture agitation of the tank without baffles.