CFD Models as a Tool to Analyze the Performance of the Hydraulic Agitation System of an Air-Assisted Sprayer

Abstract

A computational fluid dynamics (CFD) model of the fluid velocities generated by the agitation system of an air-assisted sprayer was developed and validated by practical experiments in a laboratory. The model was developed considering different settings of the agitation system: Three water levels in the tank (1000, 2000, and 3000 L); two different numbers of active nozzles (2 or 4); and three working pressures of the agitation circuit (8, 10, or 12 bar). Actual measurements of the fluid velocity into the tank were taken using an acoustic Doppler velocimeter (ADV). CFD simulations made it possible to estimate fluid velocities at 38% of the measuring points with relative errors of less than 30%. Additionally, the CFD models have allowed the correct prediction of the general behavior of the fluid in the tank considering mean velocities depending on the setting parameters of the agitation system (water level in the tank, hydraulic circuit pressure, and number of active nozzles).

Biphasic Computational Fluid Dynamics Modelling of the Mixture in an Agricultural Sprayer Tank

“…Therefore, the source of error cannot be attributed to either the mesh or the chosen turbulence model, which has also previously been shown [11] to provide reasonable results. We can also exclude the case of an inadequate time step, because a test simulation using four working agitators with 0.5 s time steps, in which the calculation residues of the dispersed phase were less than 1 × 10 −5 ; the obtained results were very similar to those that were obtained with time steps of 1 s.…”

“…The significant error that accumulated in the calculation with four agitators might be because the streams generated in the tank (shown in Figure 8) are more complex (they involve more recirculation), so, under these conditions, the calculation errors in the dispersed phase were greater. The complex stream conditions have been studied previously [11], and they occur because the main jets collide in the breakwater holes when all of the agitators are activated, impeding an adequate exchange of fluid between the two sub-chambers of the tank. With two agitators operating, the flow runs freely through the whole tank, crossing the breakwater through its openings without any problem, as shown Figure 8; but with four agitators working simultaneously, the flows become independent in four internal recirculation cells.…”

“…This is a computer numerical calculation technique that solves problems involving fluids flows. Its most common application in the study of agricultural sprayer agitation systems has been the estimation of liquid velocities and the subsequent comparison with real values [9][10][11], the influence of different nozzle positions, orientations, and operating pressures [12], and the empirical study of concentration in the solution by correlating it with the velocities of a CFD model of a sprayer tank [13].…”

Analysis of Fluid Velocity inside an Agricultural Sprayer Using Generalized Linear Mixed Models

“…No evidence was found of the use of GLMM in the analysis of the operation of the agitation system of agricultural sprayers. Until now, studies carried out in this regard have focused on the use of linear models such as ANOVA [4] or numerical modeling using CFD [1,6]. Therefore, the GLMM application methodology proposed in this research can be extended to different tank geometries (cylindrical, asymmetric, cubic, etc.)…”

“…Different studies have investigated fluid velocities inside spray tanks using Computational Fluid Dynamics (CFD) [5]. The use of this type of model is very useful, but it has the drawback of requiring long calculation times and the need for very precise data on the geometry of the interior of the tank and the location and characteristics of the components of the agitation system [6]. In this sense, Generalized Linear Mixed Models (GLMM) are an alternative to the CFD.…”