Multi-Physics Coupling Mechanisms and Coordinated Control in UAV-Based Centrifugal Spraying Systems: A Review

Centrifugal spraying systems are widely used in plant protection unmanned aerial vehicles (UAVs) due to their flexible droplet size adjustment and low-volume application capabilities. These systems can typically generate a wide range of volume median diameters from 50 to over 300 micrometers depending on rotational speed and disc structure. However, field performance is governed by a complex multi-physics coupling process rather than atomizer performance alone. Droplets released from the atomizer undergo near-field expansion and are subsequently entrained by rotor downwash. While strong downwash significantly improves deep canopy penetration compared to traditional application methods, it also dynamically reshapes droplet trajectories and size spectra through high-shear wake vortices. A critical comparative gap identified in this review is the severe discrepancy between static indoor atomization models and dynamic field transport. Current research lacks continuous spatial-temporal tracking of droplet size spectra under these complex field conditions. To address this, this review synthesizes the continuous mapping among droplet generation, spray plume transport, and canopy deposition. Precision application requires coordinated matching of flight parameters, aerodynamic downwash, and canopy architecture rather than single-parameter optimization. Future research must focus on the dynamic reconstruction of droplet size spectra and multisource perception-based feedback to shift centrifugal spraying systems from empirical parameter adjustment to mechanism-driven, closed-loop coordinated control.