Numerical Simulation Of The Flow Field Characteristics And Pesticide Selection Of The Spray Nozzle In The Tea Garden Of UAV

With the aging of population and the intensification of urbanization,compared with other plant protection devices,the safe,flexible and efficient plant protection UAV is obviously more suitable for plant protection operations in tea plantations.However,there are great challenges in the application of UAVs in plant protection in tea plantations.First of all,since tea plantations are mostly distributed in hills and mountains,the structure of downwash flow field generated during plant protection UAV operation is more complex than that in other environments.In this thesis,a six-rotor plant protection UAV is taken as the object,and the model of six-rotor UAV and nozzle is established based on the characteristic parameterized modeling method.Based on Reynolds mean N-S equation and SSTK-ω turbulence model and unstructured mesh,under hovering and flying conditions,the velocity variation of downwash flow field of plant protection UAV is numerically simulated and analyzed by using computational fluid dynamics(CFD)method.At the same time,the VOF model combined with the standard k-ε turbulence model is used to simulate and analyze the nozzle outflow field.The results provide basic work for the study on the drift and deposition distribution of pharmaceutical liquid droplets in the downwash flow field of six-rotor plant protection UAV in tea garden,and provide reference suggestions for actual plant protection operations.Specific work is as follows:1)According to the in-depth analysis of the composition structure of the six-rotor plant protection UAV,the model of UAV is established.The basic theoretical knowledge based on CFD numerical simulation method is introduced,and corresponding governing equations,discrete schemes,turbulence models and calculation methods are presented.2)Based on the CFD numerical simulation method,under the left wind condition of1.8m/s,the downwash flow field changes of the six-rotor plant protection UAV at the height of 1.5m and 2m were numerically simulated with the rotor speed reaching the hovering state of 300rad/s,400rad/s and 500rad/s,respectively.The results show that,at the same hover height,the rotor speed of 300rad/s and 400rad/s is more suitable than 500rad/s;At the same rotor speed,hovering height of 2m is more suitable than 1.5m.3)Based on the CFD numerical simulation method,under the left wind conditions of1.8m/s,the washing field changes of the six-rotor plant protection UAV flying at the height of 1.5m and 2m at 3m/s and 5m/s respectively were numerically simulated.The results showed that,at the same flight speed,2m flight height was more suitable for the practical application of the UAV spray in the tea plantation.The flight speed of 3m/s is more suitable than 5m/s at the same flight altitude.4)Based on the constant influence of the downwash flow field structure on droplets of pharmaceutical liquid under hovering state of UAV,the selection of nozzles and pesticides in tea plantation was optimized.The numerical simulation results were compared with the experimental results of Vallet and the measurement results of particle imaging velocimetry(PIV)on the performance of spraying pesticide with nozzle,the reliable numerical simulation results are obtained.The results show that: when using FPV110-02 nozzle,the concentration of 1:1000 bifenthrin is more suitable;the KZ80-04 nozzle is most suitable when using a 1000 times dilution of bifenthrin.