Influence of crosswind on droplet drift of flat-fan nozzle in aviation plant protection UAV

Objective  Crosswind is the main factor affecting droplet drift and spraying effect of aerial spraying for plant protection unmanned aerial vehicle (UAV). To explore the influence of crosswind on droplet deposition and drift during aerial spraying, and provide data support and theoretical guidance for selection of operation parameters and improvement of key components of aerial spraying for plant protection UAV.

Method  Lechler series LU 120-015 and LU 120-03 standard fan-shaped pressure nozzles were taken as the research objects. Based on the particle tracking technology of computational fluid dynamics (CFD) discrete phase model, the simulation tests of droplet flow field and pesticide spraying discrete phase in the wind tunnel were carried out under suitable boundary conditions. Through the simulation, the deposition and drift distribution of droplets sprayed by fan nozzle were analyzed visually to explore the drift characteristics of droplets at different lateral wind speeds. The deposition and drift characteristics of droplets were tested and analyzed in the agricultural aviation special wind tunnel under the similar conditions.

Result  The simulation results showed that the drift degree of discrete phase droplets was more serious and the horizontal drift of droplets was more obvious with the increase of lateral wind speed. With the increase of lateral wind speed, the accurate deposition rate (R_a) decreased exponentially from 14.11% to 0.66%, and the horizontal drift rate (R_h) increased linearly from 14.25% to 60.58%. The wind tunnel test results showed that the R_h values of droplets were 0.4%, 48.1% and 75.1% at the lateral wind speeds of 1, 3 and 6 m/s respectively, and the droplets appeared the winding phenomenon to a certain extent in the wind tunnel. The results of correlation analysis showed that there was a significant correlation between the horizontal drift rates of computer simulation and wind tunnel test, and the R² was 0.963 (P<0.05).

Conclusion  The simulation test has a good prediction effect on droplet drift under aerial spraying condition. The simulation-assistanted wind tunnel test method can get a reasonable result of the droplet deposition and drift of the flat-fan nozzle commonly used in aviation plant protection operation.