Abstract
In recent years, multirotor unmanned aerial vehicles (UAVs) have become more and more important in the field of plant protection in China. Multirotor unmanned plant protection UAVs have been widely used in vast plains, hills, mountains, and other regions, and become an integral part of China’s agricultural mechanization and modernization. The easy takeoff and landing performances of UAVs are urgently required for timely and effective spraying, especially in dispersed plots and hilly mountains. However, the unclearness of wind field distribution leads to more serious droplet drift problems. The drift and distribution of droplets, which depend on airflow distribution characteristics of UAVs and the droplet size of the nozzle, are directly related to the control effect of pesticide and crop growth in different growth periods. This paper proposes an approach to research the influence of the downwash and windward airflow on the motion distribution of droplet group for the SLK-5 six-rotor plant protection UAV. At first, based on the Navier-Stokes (N-S) equation and SST k–ε turbulence model, the three-dimensional wind field numerical model is established for a six-rotor plant protection UAV under 3 kg load condition. Droplet discrete phase is added to N-S equation, the momentum and energy equations are also corrected for continuous phase to establish a two-phase flow model, and a three-dimensional two-phase flow model is finally established for the six-rotor plant protection UAV. By comparing with the experiment, this paper verifies the feasibility and accuracy of a computational fluid dynamics (CFD) method in the calculation of wind field and spraying two-phase flow field. Analyses are carried out through the combination of computational fluid dynamics and radial basis neural network, and this paper, finally, discusses the influence of windward airflow and droplet size on the movement of droplet groups.
Highlights
There is considerable impetus to find new effective plant protection machinery, due to the limitation of ground equipment and the shortage of agricultural labor force, caused by low production efficiency and reduction of rural populations
The influence of downwash airflow, windward airflow, and particle size on the motion of droplet groups are studied for the SLK-5 six-rotor plant protection
Based on the k–ε turbulence model, the three-dimensional downwash airflow on the motion distribution of droplet groups are studied for the SLK-5 six-rotor plant protection numerical model is established for the unmanned aerial vehicles (UAVs) under 3 kg load condition
Summary
There is considerable impetus to find new effective plant protection machinery, due to the limitation of ground equipment and the shortage of agricultural labor force, caused by low production efficiency and reduction of rural populations. Multirotor UAV spraying involves small scale local complex wind fields caused by the opposite rotational speed of adjacent rotors. CFD has been widely used in aerospace, internal combustion engine, automotive, and other fields This method can accurately capture the flow details of the spraying process and compensate for the lack of AGDISP and AgDRIFT models in multirotor UAV spraying. The CFD simulation of droplet trajectories, presented in this paper, is based on our previous study [17], where a three-dimensional CFD model of the downwash airflow was established for the SLK-5 multirotor plant protection UAV, in which the vertical and horizontal speed distribution of Energies. 5, the the work work is summarized, summarized, and conclusions airflow, and droplet size, a drift prediction model is established for the six-rotor plantand protection are made. When the lift generated by the rotors and the UAV gravity are equal, the UAV will be in a hover state
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