Alternatives of implementation of hydropneumatic sprayers in numerical models of computational fluid dynamics

The analysis of phytosanitary treatments using computer numerical models is interesting to improve their efficiency, with advantages over the experimental study. The first step to perform these numerical models is to model the treatment carried out by the sprayer. In the case of air-assisted sprayers, which generate air jets, there are different alternatives to simulate the air flow supplied by the machine in CFD models: 1) introducing in the model the measured air flow at the nozzles outlet; 2) introducing in the model velocities of air measured along a line at a given distance from the nozzles; 3) modelling the exact geometry of the pneumatic circuit of the sprayer and introducing the air flow at the entrance of the circuit. The described methodologies have been tested by implementing CFD models considering an air-assisted sprayer adapted to vine crop. The methodologies based on the introduction in the model of air measurements at the nozzles outlet, validated by the literature in other types of sprayers, have not given satisfactory results in this case. The methodology based on the geometry of the machine has produced an acceptable precision. On the other hand, it presents a complexity in the meshing that makes calculation difficult. It is proposed that, in sprayers that have to be modeled in this way, the CFD calculation should be divided into several steps, separating the machine from the surrounding air.