ARS | Publication request: Using Computational Fluid Dynamics to Predict Damage of a Biological Pesticide during Passage through a Hydraulic Nozzle

Submitted to: Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 1, 2005
Publication Date: July 1, 2006
Repository URL: http://hdl.handle.net/10113/16130
Citation: Fife, J.P., Ozkan, H.E., Derksen, R.C., Grewal, P.S. 2006. Using Computational Fluid Dynamics to Predict Damage of a Biological Pesticide during Passage through a Hydraulic Nozzle. Biosystems Engineering. 94(3):387-396.

Interpretive Summary: Most commercial sprayers operate at high flow volumes and high pressure conditions which could potentially harm Entomopathogenic nematodes (EPNs) or other biological agents. The number of sprayer components that are available in the marketplace make it impossible for producers of EPNs, to test the viability of their organisms through each component or device. A computer modeling approach was studied to determine if it was possible to predict the damage to a biological agent when simulating flow through sprayer components. For these flow tests, a flat fan nozzle was chosen as the test component since it contains some of the smallest passageways on a sprayer. Bench-top experiments were also conducted to observe the effect of passage through the fan nozzle on four different EPN species. Using viability data from bench-top experiments, a model was developed to relate the observed EPN damage to the average energy dissipation rates within the nozzle predicted by the fluid dynamics models. The model as successfully able to predict relative EPN damage to within 5% of actual rates for most of the flow conditions and nematode species evaluated. All damage estimates were within 10% of observed rates of damage. The results of this study demonstrate that it is feasible to use computer modeling techniques to evaluate flow field conditions within sprayer components and to determine compatibility of that component with delivery of biological agents. Spray equipment manufacturers and producers of biological agents can use this information to optimize equipment choices to achieve the greatest possible viability of the agents and enhance the success of pest management programs.

Technical Abstract: Computational fluid dynamics (CFD) models can be used to simulate complex flow through sprayer components. Since biological organisms run the risk of being damaged during passage through components of conventional sprayers, it is critical to affirm whether or not they can be delivered using standard equipment. A CFD model approach was proposed as a means of determining the compatibility of different components with biological organisms. Flow of spray solution through a small, conventional, flat fan nozzle with an elliptical orifice was evaluated. Bench-top experiments were conducted to determine the viability of entomopathogenic nematodes (EPNs) the nozzle modeled with the CFD programming. Viability was quantified by counts of living and dead EPNs. An empirical model was developed relating EPN damage as a function of the energy dissipation rate. CFD models and bench-top experiments were conducted at several different flow rates. Four different EPN species were tested in the bench-top experiments including Heterorhabditis bacteriophora, H. megidis, Steinemema carposcapsae, and S. glaseri. The empirical model was calibrated for each of the EPN species. In general, the model was able to predict EPN damage within 5% of actual observations. The results from this study show that the CFD approach could be used to identify flow field conditions within various sprayer components that might potentially damage biological organisms.