| In order to obtain soybean field after sealing ridge rotor eppo unmanned aerial vehicle(uav)droplets deposition effect better and to improve the working process of the plant protection level of prevention and control of plant diseases and insect pests,this paper with the method of CFD numerical simulation and laboratory test study the multiple uav rotorcraft hovering downwash flow and the interaction mechanism of the droplets and soybean canopy,to provide scientific theory basis for eppo uav soybean field operation parameters optimization basis.The main research work is as follows:1)Study on the distribution of UAV rotor wind field and airflow-assisted droplet deposition theoryAccording to the principle of relative statics in fluid mechanics,the formation reasons of the upward force and wind field distribution of multi-rotor UAV were explored.It was found that the main factors determining the wind field distribution were the rotor geometry,the pressure difference between upper and lower surfaces,the rotor speed and the height.The movement process of fog drops under the action of rotor wind field is analyzed.Combined with air drag force,pressure difference force,Basset force,Magnus force and Saffman force,it is proved that the deposition process of fog drops is mainly affected by rotor wind speed,movement time and distance.It provides a basic theoretical support for CFD numerical simulation of droplet deposition distribution caused by hovering washing airflow of multirotor plant protection UAV and soybean canopy.2)Effects of hovering washing airflow of multi-rotor plant protection unmanned aerial vehicle on soybean canopy based on CFDIn order to study the interaction between UAV hovering down wash airflow and soybean plant,an efficient calculation region of UAV hovering flow field was established based on Reynolds average equation,combined with RNG k-ε model and unstructured grid,and a soybean pod model was established by using the method of static porosity similarity.Respectively explores the presence of soybean plant rotor speed under the condition of 300～500 rad/s interval hovering downwash flow distribution,the hovering downwash flow field distribution is obtained due to the differences of soybean canopy influence rule,namely the influence of the soybean plant,rotor wind field in access to the soybean plant canopy,speed starting to wane,then speed and pressure size obvious ups and downs,The wind field in the canopy is relatively dispersed,and the velocity of the airflow when it reaches the height of the crop canopy ranges from 1 to 3.5m/s.3)Interaction mechanism of multi-rotor plant protection unmanned aerial vehicle under hovering wash and fog drops based on gas-liquid two-phase flowBased on the Fluent discrete phase model,the gas-liquid two-phase flow interaction between the hovering downwash flow and fog drops of a multi-rotor plant protection UAV was analyzed,and the complex motion process and trajectory of the coupling field of fog drops under the action of the rotor downwash flow field were explored.The spatial distribution of single and multiple droplets under different rotor speeds was compared respectively,and the internal movement trajectories of droplets under different rotor speeds were analyzed with emphasis,so as to explore the deposition movement characteristics of droplets assisted by downwash airflow in the soybean canopy.The numerical simulation results show that the distribution uniformity of droplet deposition is poor when the rotor speed is 300rad/s in the spray simulation of the soybean plant model.When the rotor speed is 400rad/s,the distribution uniformity of droplet deposition is good.When the rotor speed is 500rad/s,the distribution uniformity of droplet deposition is general.With the increase of spraying time,the overall droplet distribution has little difference.The rotor downwash airflow and soybean canopy have a great influence on the movement of droplets.From the perspective of the overall and individual droplet trajectories and droplet concentrations under different rotor speeds,the droplet deposition distribution is relatively good when the rotor speed is 400rad/s.4)Experimental study on the influence of washing flow field and soybean canopy on droplet movement under hover of multi-rotor plant protection UAVA multi-rotor plant protection UAV test rig was designed to test the overall wind field distribution of the model with or without soybean plants,the wind field distribution at different heights,and the wind field inside the canopy of soybean plants,etc.,and to compare and analyze the simulation results above to analyze the variation of errors.Through indoor spray test,the spray uniformity of droplet deposition under different rotor speeds was compared with the simulation results,and the results of laboratory test were consistent with the simulation results.The velocity distribution of planes at different heights and the velocity distribution of simulation show obvious symmetrical distribution.While the Z-direction velocity decreases from top to bottom,the range of velocity contour line becomes larger and larger.Wind field changes at different heights in the soybean canopy showed that the upper wind speed reached a maximum of 2.7m/s and a minimum of 0.3m/s. |
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