Numerical simulation analysis and experimental research on liquid sloshing in herbicide tank of the plant protection UAV

The sloshing of the liquid inside the herbicide tank of a plant-protection unmanned aerial vehicle (UAV) is a key factor affecting the stability and safety of UAV operations. To address this issue, this study analyzed the sloshing behavior of the liquid by employing flight tests and simulations to reveal the intrinsic characteristics of the sloshing liquid. An attitude monitoring system for the herbicide tank was constructed to collect acceleration signals during the plant protection UAV operation, and a corresponding model was developed to conduct simulations. The results indicate that the simulations based on the finite volume method were consistent with the experimental results, with the correlation coefficients of the captured free-surface curves exceeding 0.89. During the acceleration stage, the liquid exhibited periodic swaying. In the sudden stop stage, the free surface overturned, generating a large number of bubbles and vortices inside the liquid. This changed the direction of liquid flow, sloshing force, and sloshing mode of the free liquid surface, with the accumulation and collision of the liquid at the wall and corners becoming more significant. Under the turning condition, the liquid transitioned from counterclockwise swirling to swaying, but the amplitude of the liquid sloshing was reduced compared with the sudden stop condition. In summary, this study explored the sloshing process in the herbicide tank of a plant protection UAV based on sensor technology and computer numerical simulations, providing insights for the optimization and upgrading of equipment for plant protection UAV.