Research On Air Flow Field Distribution And Fog Drop Penetration Of UAV Rotor Wing Based On CFD

The spraying of pesticides by drones has gradually been promoted in field pest control operations.Compared with traditional plant protection machinery,the use of drones for spray operations has many advantages.For example,when using a ground sprayer to work among fruit trees,it will face problems such as terrain restrictions and dense planting of fruit trees,resulting in low operation efficiency and poor control of diseases and insect pests.In recent years,researchers from various countries have done a lot of research on drone prevention and control of fruit trees.Many of them focus on the effect of drone operation parameters and body structure design on the deposition of fog droplets on the canopy of fruit trees.Regarding the research on the downwash airflow field of UAV rotors,the numerical simulation of the airflow field distribution of UAV rotors is often conducted.Or use porous media instead of crop canopy for simulation,and analyze the distribution characteristics of airflow field in the presence of fruit tree canopy.Because the porous media is very different from the real tree in shape and structure,the results of simulation analysis often lack reliability.In this paper,based on the current status of UAV plant protection research,a three-dimensional model that reflects the real peach tree to a large extent is established,and the distribution characteristics of the UAV rotor airflow field in the presence of fruit tree canopy are developed.Finally,according to the penetration of fog droplets in the canopy of fruit trees,field experiments were conducted to analyze the influence of various influencing factors on the penetration of spray droplets of drone in the canopy of fruit trees.The main contents of this article are as follows:The beginning of this thesis expounds the current pest control in my country,the application status of drone plant protection at home and abroad,and the research on drone spray droplets,and puts forward the research content of this article.That is,the distribution characteristics of the drone rotor airflow field in the presence of fruit tree canopy and the field experiment to analyze the effects of operating height,operating speed and nozzle flow rate on the penetration of spray droplets between fruit tree canopy.It shows that the research content of this article has certain practical significance and value.The secondly chapter of this paper introduces the basic theory of computational fluid dynamics and the calculation process of simulation,including control equations,discretization methods,turbulence models,sliding grid technology,selection and setting of boundary conditions,and algorithm selection.Combined with the actual situation of the air flow field generated by the simulation of the rotation of the UAV rotor,the appropriate conditions and parameters are set for the simulation process in this paper.The third chapter firstly introduces the commonly used three-dimensional tree modeling methods,analyzes and summarizes the advantages and disadvantages of each method,and proposes the three-dimensional tree modeling method used in this article.This article uses VBA programming language to control Auto CAD drawing software to generate the structure of each part of the tree.This modeling method is simple,the model generation efficiency is high,and the true structural characteristics of the tree body can be more realistically restored.Provide better tree model for subsequent simulation.The fourth chapter firstly introduces the main structural parameters of the DJI T16 plant protection UAV selected for the experiment,and emphasizes the special rotor rotation direction of the DJI T16 UAV.Based on the fluid dynamics theory in Chapter 2,using ANASY ICEM CFD meshing and FLUENT simulation software,the three-dimensional peach tree model established in Chapter 3 is brought into the UAV rotor flow field for simulation and simulation.The UAV rotors are located 1.5m,2m,and 2.5m from the top of the peach tree,respectively.After the calculation is completed,intercept the vertical wind velocity clouds on the horizontal planes of2.3m,1.5m,and 0.8m from the ground of the peach tree,and then select the X axis on these three planes.The X-YPlot parameters of these three axes in FLUENT will be selected.Import into Tecplot for post-processing,get the vertical velocity curve along the X axis in these three horizontal planes.According to the vertical speed curve,when the drone hover height is 4.3m,the maximum vertical wind speed on the X axis on the 2.3m plane of the peach canopy is 11.9m/s;on the 1.5m plane of the peach canopy The maximum vertical wind speed on the X axis is 6.1m/s;the maximum vertical wind speed on the X axis on the 0.8m plane of the peach canopy is 2.9m/s.Finally,through the wind field test,the vertical wind speed value table of the above planes along the X axis direction is obtained.Compared with the simulation results,the numerical simulation results are slightly larger than the test results in the range of X from-1.5m to-1m,but the speed difference does not exceed 0.5m/s.Therefore,it is verified that the simulation results can reflect the vertical wind speed of the real flow field.Chapter 5 mainly analyzes the penetration of fog droplets between the canopy of fruit trees under the conditions of various factors and levels through field experiments.Orthogonal test method was used to set up nine experimental groups with three factors: drone operating speed,operating height and nozzle flow under different levels.According to the formula,the droplet penetration of each group is calculated.Combining the results of the extreme analysis of the droplet deposition density and the extreme penetration analysis of the droplet penetration,the experimental group No.2 is the nozzle with a flow rate of 0.3L/min,an operating height of 2m,an operating speed of 4m/s,and droplet penetration 24.67% and the experimental group No.8nozzle flow rate is 0.5L/min,working height is 2m,working speed is 3m/s,and droplet penetration is 21.5%,the droplet penetration value of these two groups is relatively small,Good penetration.In addition,the droplet deposition density of the upper,middle,and lower layers is also ideal.These two sets of better operation plans will provide a reference for the future Peach Tree UAV plant protection operations.