Model And Experimental Study Of Droplet Drift And Deposition Based On Rotor Flow Field Of UAV

the droplets are affected by the flow field were caused the driftduring the spray operation of single and four-rotor drone.Accurately describing the rotor flow field is the premise for predicting the motion trajectory of the droplets under the washing flow field under the rotor plant protection drone.The objective of this study is to find out the influence of wing tip vortex flow of the drone on the droplet drift,a numerical simulation of the flow field under the drone was established based on an adaptive thinned physical model of the LBM method.In this method,the lattice Boltzmann equation was selected as the solving equation,and turbulence model adopted the large-eddy simulation,and the wall-modified large eddy simulation(WMLES)method was used as the boundary condition which was modeled by the wall function.The physical models of single-rotor and quad-rotor plant protection drones were established accurately.For the purpose of accurately capturing the drift of droplets of different particle sizes in the wash down the flow field of the drone due to the wingtip eddy currents,a discrete Lagrangian phase particle tracking method was used to simulate different particles diameter drop trajectory.To verify the accuracy of the numerical simulation,the research group conducted an outdoor test.Mainly reflected in the following aspects:(1)The flow field characteristics of single-rotor and quad-rotor UAVs at flight speeds of 1 to 7 m / s and different flight heights are studied.Accurately capture the wingtip vortex of the drone and the horseshoe tail vortex of the drone in the downwash field.A detailed mathematical analysis of the drone’s flow field is performed.The results show that a singlerotor plant protection drone with a flight speed greater than 3m / s can form a horseshoeshaped wake at the rear of the fuselage,and a four-rotor plant protection drone with a flight speed greater than 5m / s form a horseshoe-shaped wake at the rear of the fuselage.(2)The Lagrange discrete phase particle tracking method was used to simulate the trajectories of droplets with different particle sizes.By changing the flying speed,flying height,the horizontal distance between the boom height and the nozzle,the influence of these conditions on the deposition and drift of the droplets behind the fuselage was studied.Numerical simulations and experiments show that the speed of single-rotor UAVs is 2m / s,5m / s,7m / s,and the drift heights are 2.92 m,3.54 m,3.62 m.And the spacing distance of the nozzle position is 0.1m,the vertical height of the boom is 0.55 m,and the drift height is 3.39 m and 3.48 m.The results show that the flying speed and flying height have a significant impact on the droplet trajectory,and the lateral distance between the boom height and the nozzle has a relatively low effect on the droplet trajectory.(3)The accuracy of the numerical simulation was verified by field tests and wind tunnel tests.The numerical simulation results are in good agreement with the experimental data.The best operating parameters are a flying speed of 2m / s,a flying height of 1m,a boom height of 0.25 m,and a nozzle spacing of 0.4m.The results show that the mathematical model of droplet drift and flight speed,flight height,boom height,and lateral distance between nozzles fitted through field tests and wind tunnel tests has higher accuracy.And the experimental data verify that the accuracy of the numerical analysis is high.