SBIR/STTR Award attributes
There is an intense need for aerial spray application nozzles that are able to produce quality spraycoverage while minimizing losses to spray drift. Aerial nozzles that are used for application ofcrop protection materials to the ground are usually chosen for their ability to produce coarserdroplets with the smallest possible volume fraction of droplets below 150 microns. This is oftencalled the "driftable fraction". Since most nozzles were originally designed for use in low-speedterrestrial based applications their external design and how it interacts aerodynamically with airflowing around it was generally irrelevant or even optimized for use with no or low speedflowing over it. In aerial spray applications especially at high speeds the aerodynamicconditions around the nozzles represent much higher forces and as such can significantly impactthe performance of the nozzles. Surprisingly to date there has been no effort to redesign andoptimize these nozzles to streamline and optimize the flow of air over their exterior surfaces. It isa well-known phenomena that any fluid (air being a fluid) passing over a sharp edge or transitionwill create turbulent eddies on the lee side of the edge. At high enough velocities such as thosefound in aerial spray application the energy contained in these eddies can be of enoughmagnitude to contribute to irregular droplet formation in the spray jet leading to an increase indriftable fraction.Phase I of this project will use Computational Flow Dynamics software in conjunction withprinciples of aerodynamic flow to modify the exterior surfaces of existing straight stream and flatfan nozzle designs and the hardware designed to hold them. It will then show in high speed windtunnel air conditions such as those experienced during spray application that the driftablefraction can indeed be reduced by incorporating designs that smoothly meld the transitionsbetween surfaces and carefully managing the airflow as it interacts with the spray jet. In Phase IIthis will be refined further in a wider range of operational conditions again using ComputationalFluid Dynamics (CFD) software to simulate and optimize the designs before final in-situ aerialtesting and creation of the final product. The ultimate product of this project will be a nozzlesystem that improves aerial applicators' ability to manage drift risk in aerial applications withlower drift in a broader range of weather conditions while still maintaining an efficacious spraydroplet spectrum.
