The project aimed to improve the efficiency of aerial chemical defoliation in the Australian cotton industry. With newer cotton varieties developing denser canopies, achieving complete defoliation in fewer passes has become increasingly difficult. This results in higher chemical usage, increased operational costs, and a greater risk of spray drift. The research focused on understanding the aerodynamic and environmental factors affecting spray penetration to optimize application efficiency and improve defoliation outcomes.

Using Computational Fluid Dynamics (CFD) analysis, the study identified turbulent kinetic energy (TKE) and particle z-velocity as key factors influencing spray deposition. TKE was found to be the dominant driver of deposition at the top of the canopy, and optimizing for TKE, despite slightly reducing particle z-velocity, still led to an overall improvement in spray effectiveness. The study highlighted that spray boom configurations, particularly nozzle settings, had the greatest impact on canopy penetration, making them a more effective focus for optimization than pilot-controlled flight adjustments.

For the AT802A aircraft, specific nozzle configurations, including increasing flat fan angles, using smaller orifice nozzles, and incorporating a 12° deflection angle, were shown to significantly enhance canopy penetration and deposition. The study recommends validating these changes using the USDA droplet model before implementation to ensure their effectiveness in real-world conditions.

Despite challenges in modelling a 3D plant canopy, the research validated current aerial application practices and confirmed the reliability of existing spray models for optimization. It also showcased the potential of multiphase CFD for future advancements in aerial spray techniques.