Objective To enhance the application performance of unipolar contact electrostatic spraying technology in agricultural plant-protection unmanned aerial vehicles (UAVs), this study investigates droplet deposition characteristics under different crosswind and height conditions,aiming to optimize the spray system design,improve pesticide utilization,and reduce environmental pollution.

Method A computational fluid dynamics (CFD) discrete phase model combined with user-defined functions (UDF) was developed to simulate the electrostatic spray field.A charge-to-mass ratio measurement platform was used to obtain droplet charge-to-mass ratios under different voltages as the initial model parameters. The deposition characteristics of droplets for the unipolar contact-type electrostatic spraying system, under different wind speeds and spraying heights were analyzed through simulation, and the model was validated by outdoor experiments.

Result Simulation results showed that within the spraying height range of 1.5–1.8 m, electrostatic spraying achieved more uniform deposition and smaller crosswind drift compared with conventional spraying. At 1.5 m, the liquid film distribution was stable and less affected by wind speed. At 1.6 m, when wind speeds were 2 m/s and 3 m/s,the liquid film peak decreased by 25 μm and 34 μm,respectively,compared with 112 μm at 1 m/s.At 1.8 m,the liquid film peak under all wind speeds decreased by 25.9%, 26.3% and 17.3%, respectively, compared with that at 1.5 m. Outdoor experiments further demonstrated that the center-of-mass distance of electrostatic spraying was reduced by 13.05%compared with conventional spraying.

Conclusion The unipolar contact electrostatic spraying system applied in agricultural UAVs exhibits excellent droplet deposition performance.The simulation results are consistent with outdoor experimental deposition trends, providing theoretical basis and practical guidance for the optimization of aerial electrostatic spraying technology and precision agriculture.