Using Computational Fluid Dynamics to predict Damage of a Biological Pesticide during Passage through a Hydraulic Nozzle

The wide variety of agricultural spray equipment commercially available makes it difficult to test equipment components for compatibility with biological pesticides under varying operating conditions. One approach to this problem is to use computational fluid dynamics (CFD) as a tool to numerically simulate the complex flow conditions within different equipment components. From the numerical simulations, the flow-field parameter energy dissipation rate is used to characterise local hydrodynamic conditions potentially resulting in organism damage. Experimental tests measured damage to a benchmark biological pesticide, entomopathogenic nematodes (EPNs), after being passed through a standard flat fan nozzle (Spraying Systems XR8001VS) and hollow cone nozzle (Spraying Systems TXA8001VK) at varying flow rates. Numerical simulations of the internal flow for each nozzle were performed for the experimental flow conditions. An empirical model relating EPN damage as a function of the computed average energy dissipation rate was developed using data from a previous study. The model was validated using experimental and numerical results from the nozzles. Overall, the model was able to predict EPN damage well, in many cases within 5% of observed rates of damage. The results from this study show that CFD is a feasible method to evaluate spray equipment and operating conditions for delivery of biopesticides.