Method for continuously impacting and buffeting leaf surface model by pesticide fog drop groups at different azimuth moments

Abstract

The invention discloses a method for continuously impacting and buffeting a leaf surface model by a pesticide fog drop group at different azimuth moments. The method comprises the following steps: S1, constructing a three-dimensional multi-fog-drop static simulation model; s2, determining an optimal multi-pesticide droplet impinging phase interface tracking method, an optimal surface tension model and an optimal grid establishment method; s3, optimizing a grid, and locally refining a pesticide fog drop generation area; s4, constructing a multi-pesticide droplet impact simulation model based on the actual dynamic wall surface; s5, editing a user-defined function, and controlling generation of multiple pesticide fog drops and leaf surface vibration; and S6, carrying out numerical research on dynamic behavior change of collision of multiple pesticide droplets on the real leaf surface. According to the method, a control strategy based on a user-defined function is adopted, the generation time, position and number of pesticide droplets are adjusted, an interface tracking method and a surface tension model are combined, and the movement process of the pesticide droplets on a dynamic wall surface is simulated.

Description

Technical Field

[0001] The invention relates to the intersection of computational fluid dynamics and pesticide spraying, and in particular to a method for pesticide droplet groups to continuously impact a vibration leaf surface model at different positions and times. Background Art

[0002] Existing agricultural spraying technologies face challenges in dealing with different crop heights, vegetation densities, and terrain changes. In particular, it is particularly difficult to maintain the uniformity and effectiveness of spraying in irregular terrain or under conditions of changing wind. In addition, traditional systems are limited in response speed and adjustment accuracy, and it is difficult to adapt to environmental changes in real time, which limits their application in efficient and sustainable agricultural production. Specifically, in terms of simulation, traditional methods find it difficult to achieve precise control of droplets in continuous time series and multi-directional spatial distribution in a dynamic environment, resulting in deviations between simulation and actual spraying scenarios. If a large time difference is required between pesticide droplets, a height difference needs to be set to meet the interval time, which requires a large computational domain and grid, and a large amount of calculation. Summary of the invention

[0003] The purpose of the present invention is to provide a method for continuously impacting a vibration leaf surface model at different positions and times of a pesticide droplet group. By adopting a control strategy based on a user-defined function (UDF), the present invention can simulate the impact behavior of multiple droplets at continuous time and multiple positions (such as different horizontal spacing, impact angles, and heights) through a user-defined function (UDF), significantly improving the consistency between the simulation and the actual spraying scene. In addition, the present invention further improves the simulation accuracy by optimizing the grid and locally refining the pesticide droplet generation area, ensuring accurate simulation of key parameters such as the spreading speed and wall pressure after the pesticide droplets hit the wall.

[0004] In one aspect of the present invention, the present invention proposes a method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times. According to an embodiment of the present invention, the following steps are included:

[0005] S1. Construct a three-dimensional multi-droplet static simulation model;

[0006] S2, determine the best multi-pesticide droplet impact phase interface tracking method, surface tension model and grid establishment method;

[0007] S3, optimize the grid and locally refine the pesticide droplet generation area;

[0008] S4. Construct a multi-pesticide droplet impact simulation model based on actual dynamic wall;

[0009] S5, editing a user-defined function to control the generation time, orientation and leaf vibration of multiple pesticide droplets, wherein the orientation includes the horizontal position, height and angle of impact of the pesticide droplets on the leaf surface;

[0010] S6. Numerical study on the dynamic behavior changes of multi-pesticide droplet impact on real leaf surface to verify the feasibility of multi-pesticide droplet impact simulation model.

[0011] In addition, the method for continuously impacting the buffeting leaf surface model with a group of pesticide droplets at different positions and at different times according to the above embodiment of the present invention may also have the following additional technical features:

[0012] In some embodiments of the present invention, in step S1, the construction of the three-dimensional multi-droplet static simulation model specifically includes the following steps:

[0013] S101, selecting the type of pesticide and measuring the physicochemical parameters of the pesticide required for numerical simulation;

[0014] S102, setting the spatial dimension parameters, calculation boundary conditions and regional conditions of the simulation model;

[0015] S103, setting droplet parameters in the simulation model.

[0016] In some embodiments of the present invention, in step S101, the physicochemical parameters of the pesticide agent include the surface tension, viscosity, and density of the pesticide agent droplets; in step S102, the calculation boundary conditions include the initial temperature, operating pressure, boundary inlet and outlet conditions of the entire calculation domain of the simulation model, and the regional conditions include the initial regional distribution of each phase; in step S103, the droplet parameters include the size parameters and position parameters of the droplets.

[0017] In some embodiments of the present invention, in step S2, a continuous surface force and volume fraction coupling calculation model, a continuous surface stress and volume fraction coupling calculation model, and a continuous surface force and volume fraction corrected zero isosurface coupling calculation model are selected as a multi-pesticide droplet impact phase interface tracking method and surface tension model.

[0018] In some embodiments of the present invention, in step S2, three grid sizes are set: the overall calculation domain grid size, the leaf impact grid size, and the pesticide droplet generation area grid size.

[0019] In some embodiments of the present invention, in step S4, the construction of a multi-pesticide droplet impact simulation model based on an actual dynamic wall includes the following steps:

[0020] S401, determining a real blade model;

[0021] S402, establishing a three-dimensional calculation domain of the impact site;

[0022] S403, setting impact simulation calculation boundary conditions according to the physical and chemical parameters of the real leaves and the pesticide spraying conditions.

[0023] In some embodiments of the present invention, step S5 specifically includes the following steps:

[0024] S501, setting a simulation device for pesticide droplets impacting leaf surfaces;

[0025] S502, determining the initial position, initial velocity, and impact angle of the pesticide droplets;

[0026] S503, measuring the vibration shape function of the leaf surface required for numerical simulation by simulating the impact of mist droplets on the leaf surface on the simulation device;

[0027] S504. Standardize the editing of user-defined functions to ensure that the required functions are complete.

[0028] In some embodiments of the present invention, in step S501, the simulation device includes:

[0029] An experimental stand, on which a clamping mechanism is installed, and the clamping structure is used to clamp the end of the petiole of the leaf blade;

[0030] A liquid spraying mechanism, the liquid spraying mechanism comprises an injection pump and a needle-shaped nozzle, the injection pump is connected to the needle-shaped nozzle, a nozzle is installed at the lower end of the needle-shaped nozzle, and the nozzle is located just above the center of the blade;

[0031] Piezoelectric ceramics, wherein the piezoelectric ceramic sleeve is installed at the nozzle, and the piezoelectric ceramics are used to generate high-frequency vibration to stabilize the spray droplet injection;

[0032] A camera, which is used to capture the process of pesticide droplets hitting the leaf surface;

[0033] An image processing module is used to process images obtained by a camera.

[0034] In some embodiments of the present invention, the piezoelectric ceramic is connected to a high-frequency power amplifier, and the high-frequency power amplifier is respectively connected to an arbitrary waveform generator and an oscilloscope. The arbitrary waveform generator is used to send a piezoelectric drive signal to the high-frequency power amplifier, and the high-frequency power amplifier is used to amplify the piezoelectric drive signal and drive the piezoelectric ceramic to vibrate at high frequency. The oscilloscope is used to display the drive waveform signal amplified by the high-frequency power amplifier.

[0035] In some embodiments of the present invention, in step S6, the changes in dynamic behavior include changes in the wall pressure on the blade surface after the real leaf surface is impacted by the droplets during the process of the pesticide droplets impacting the real vibrating leaf surface, changes in the spreading speed of the droplets when wetting the blade surface, and changes in the flow state of the droplets at different times when the droplets fall and impact the leaves.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1) The accuracy of multi-pesticide droplet control is improved. In the prior art, the generation and motion control of pesticide droplets are usually limited by the initial condition setting, and it is difficult to achieve accurate control of pesticide droplets at different times, positions and angles. The present invention, by introducing user-defined functions (UDFs), can flexibly control the generation time, spatial position, impact angle and motion parameters of multi-pesticide droplets in numerical simulations. This precise control capability makes the dynamic process of pesticide droplets hitting the wall more realistic and controllable, and can adjust the spraying parameters according to the specific needs of the crop and environmental factors. For example, the direction and flow of the nozzle are automatically adjusted according to the crop height and row spacing to ensure that the pesticide and nutrient solution cover the entire target area evenly and accurately. By integrating UDF into CFD software, agricultural producers can achieve true precision agriculture in complex environments while reducing resource waste and environmental impact.

[0038] 2) The present invention takes into account the properties of the pesticides actually used and the surface conditions of real leaves, and considers the interface tracking methods and surface tension models in simulating specific production practices, and constructs two three-dimensional simulation models, using three-dimensional simulation to be closer to the actual situation.

[0039] 3) Comprehensive analysis of pesticide droplet impact behavior. The present invention can not only simulate the phase change and spreading process after the pesticide droplets hit the wall, but also analyze the changes in leaf surface pressure and pesticide droplet spreading speed over time. This comprehensive analysis of dynamic response enables the present invention to provide more dimensional reference data for the pesticide droplet impact process, and is applicable to the fields of pesticide spraying, cooling, and pesticide droplet spraying. The present invention can accurately control the pesticide droplets in the simulation to impact the moving or angled crop leaves at different times and different orientations, greatly improving the simulation of spraying accuracy and efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a flow chart of a method for continuously impacting a dithering leaf surface model at different positions and times according to an embodiment of the present invention;

[0041] Figure 2 Schematic diagram of the overall model (left figure) and the calculation domain of the impact simulation model (right figure) in an embodiment of the present invention;

[0042] Figure 3 The horizontal azimuth difference of different pesticide droplet top view angles (left figure) and the horizontal azimuth difference of the main view angle (right figure) in the embodiment of the present invention. The height difference in the right figure is mainly to better display the azimuth difference value. In the actual calculation example, the droplets generate the horizontal azimuth difference one by one at the specified position according to time;

[0043] Figure 4It is a mesh density map of different parts after local refinement of the mesh optimization in the embodiment of the present invention;

[0044] Figure 5 This is a diagram of a simulation device for pesticide droplets impacting a leaf surface in an embodiment of the present invention, in which: 1. an experimental support; 2. piezoelectric ceramics; 3. a lower clamp; 4. an injection pump; 5. a needle nozzle; 6. a nozzle; 7. a blade; 8. a high-frequency power amplifier; 9. an arbitrary waveform generator; 10. an oscilloscope; and 11. an upper clamp;

[0045] Figure 6 is a time domain displacement curve of a marking point in an embodiment of the present invention;

[0046] Figure 7 is a dynamic response curve of the blade after being hit by droplets in an embodiment of the present invention;

[0047] Figure 8 The codes of different parts of UDF in the embodiment of the present invention are intercepted. The left figure is the UDF of the pesticide droplet coordinate part, where the specific droplet coordinates are set; the right figure is the UDF of the pesticide droplet attribute part, where the specific droplet size, initial impact velocity, and angle are set;

[0048] Fig. 9 The liquid phase diagrams of multiple droplets impacting at different times after using the UDF code in the embodiment of the present invention, the numbers in the diagrams represent different times respectively, and in each group of diagrams at the same time, the upper diagram is a front view of the droplet impact, and the lower diagram is a top view of the droplet impact;

[0049] Fig.10 is a pressure curve diagram after pesticide droplet impact in an embodiment of the present invention;

[0050] Fig.11 It is a curve diagram of the spreading area after the pesticide droplets hit in the embodiment of the present invention. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 1 As shown, the method of continuously impacting the shaking leaf surface model at different positions and times of the pesticide droplet group, wherein the leaf surface is selected as the Shucha Zao leaf surface, specifically includes the following steps:

[0053] 1. Construct a three-dimensional multi-pesticide droplet static simulation model.

[0054] 1.1 Select the type of pesticide and measure the physicochemical parameters of the pesticide required for numerical simulation.

[0055] According to the experimental conditions, the types of pesticide droplets were selected as the commonly used 1:800 (dilution ratio) chlorothalonil droplets, 1:1000 malathion droplets, and 1:2500 dimethoate droplets, and the relevant parameters of the droplets of the liquid were measured. The relevant parameters include surface tension, viscosity, and density. The measurement method is as follows:

[0056] (1) Using a JYW-200B surface tension meter, the surface tension parameters of the original liquid of three kinds of liquid droplets were measured. Each liquid droplet was measured ten times, and the data with obvious artificial errors were removed, and the average value was taken as the surface tension parameter of the liquid droplet;

[0057] (2) Using an NDJ-8S digital viscometer, the viscosity parameters of the original liquid of the three liquid droplets were measured. Each liquid droplet was measured ten times, and the data with obvious artificial errors were removed. The average value was taken as the viscosity parameter of the liquid droplet.

[0058] (3) An alcohol hydrometer was used to measure the density parameters of the original liquid of the three kinds of drug droplets. Each drug droplet was measured ten times, and the data with obvious artificial errors were removed. The average value was taken as the density parameter of the drug droplet.

[0059] The parameters of the three pesticide droplets are shown in the following table:

[0060] Table 1 Parameters of three pesticide droplets

[0061]

[0062] 1.2 Set the spatial dimension parameters of the simulation 3D model. The simulation of static pesticide droplets in 3D space is used as the experimental condition to establish the 3D model. Figure 2 As shown in the figure, the shape parameters of the peripheral three-dimensional model are a cubic space area with a length, width and height of 6mm×6mm×6mm, which is the peripheral calculation domain, used to ensure that the leaf surface has enough flutter space during the simulation process; the length and width of the protruding part of the leaf surface are 2mm×2mm. The precision grid area refers to the mesh encryption of some areas, such as reducing the grid size in the area where droplets are generated, so that the surface is smooth and fine enough when the droplets are generated. The mesh of the impacted leaf surface is refined and the grid size is reduced to better observe the dynamic behavior of the droplets after impact.

[0063] 1.3 Set the boundary conditions and regional conditions for 3D simulation calculation.

[0064] The boundary conditions of the three-dimensional simulation calculation include the initial temperature, operating pressure, boundary inlet and outlet conditions of the entire calculation domain (i.e., the cubic space in step 1.2), and the regional conditions include the initial regional distribution of each phase.

[0065] In this embodiment, the initial temperature is set to room temperature 20°C; the operating pressure is set to one atmospheric pressure 101325Pa; the inlet and outlet boundary conditions are set as follows: the upper end face of the cube is set to a pressure inlet, the lower end face is set to a fixed wall, and the four sides are set to pressure outlets;

[0066] 1.4 Determine the position and size parameters of the droplets. Determine that the diameter D of the pesticide droplets is 0.3mm, the initial height of the pesticide droplets from the impacted and intercepted leaf protrusions is 0.3mm, the horizontal distance difference between different pesticide droplets is 0.5D, the subsequent generation time of pesticide droplets is 0.3ms, 1.5ms, 2.5ms, and the initial height is 0.4mm. Figure 3 shown.

[0067] 2. Determine the optimal multi-pesticide droplet impact phase interface tracking method, surface tension model and grid establishment method.

[0068] 2.1 Select the phase interface tracking method and surface tension model commonly used in the industry in recent years.

[0069] The continuous surface force and volume fraction coupling calculation model (VOF-CSF), the continuous surface stress and volume fraction coupling calculation model (VOF-CSS) and the continuous surface force and volume fraction corrected zero isosurface coupling calculation model (CLSVOF-CSF) are selected as the phase interface tracking method and surface tension model. The models used in these three methods are all available in the computational fluid dynamics simulation software ANSYS Fluent. The volume fraction method can be coupled with the continuous surface force model, and the zero isosurface and volume fraction coupling calculation method can only be coupled with the continuous surface force model. All models can be verified by papers. The volume fraction method (VOF) was proposed by Hirt and Nichols in 1981, the zero isosurface and volume fraction coupling calculation method (CLSVOF) was proposed by Sussman and Puckett in 2000, the continuous surface force model (CSF) was proposed by Brackbill et al. in 1992, and the continuous surface stress model (CSS) was proposed by Lafaurie et al. in 1994.

[0070] 2.2 In order to reduce the number of grids and ensure the accuracy of calculation, three grid sizes are set respectively: the grid size of the overall calculation domain, the grid size of the impact leaf surface, and the grid size of the pesticide droplet generation area.

[0071] 3. Optimize the grid and locally refine the pesticide droplet generation area.

[0072] 3.1 Divide the grid into three parts: fluid calculation domain, leaf impact area, and pesticide droplet generation area.

[0073] 3.2 Adjust the mesh size of the peripheral fluid calculation domain, the mesh type is tetrahedron non-standardized mesh, the mesh size is 0.2mm; locally refine the impact leaf surface area, the mesh type is tetrahedron non-standardized mesh, the mesh size is 0.02mm; insert the influence range into the pesticide droplet generation area, add the corresponding pesticide droplet generation coordinates to refine the mesh, the mesh size is 0.01mm, such as Figure 4 shown.

[0074] 4. Construct a multi-pesticide droplet impact simulation model based on actual dynamic walls.

[0075] 4.1 Import the three-dimensional multi-pesticide droplet static simulation model established in step 1 and establish the calculation domain.

[0076] 4.2 Select Material - Liquid, and set the liquid density and viscosity to the pesticide droplets measured in step 1.

[0077] 4.3 Select the continuous surface stress and volume fraction coupled calculation model (VOF-CSS) to set the droplet surface tension and initial contact angle (60°), and select the standard k-epsilon model as the viscosity model.

[0078] 4.4 According to the measured actual blade surface parameters, taking into account its surface wax layer and villi, its surface friction parameters are set to 41.5nm for the lateral friction parameter and 10.9nm for the longitudinal friction parameter.

[0079] 4.5 The boundary conditions of the three-dimensional simulation calculation include the initial temperature, operating pressure, and boundary inlet and outlet conditions of the entire calculation domain (cubic space), and the regional conditions include the initial regional distribution of each phase. In this embodiment, the initial temperature is set to room temperature 20°C; the operating pressure is set to one atmospheric pressure 101325Pa.

[0080] 5. Edit user-defined functions (UDF) to control multi-pesticide droplet generation and leaf vibration:

[0081] 5.1 Set up a simulation device for pesticide droplets impacting leaf surfaces, such as Figure 5 As shown, the simulation device includes an experimental bracket 1, a liquid spraying mechanism, a piezoelectric ceramic 2, a camera, and an image processing module.

[0082] The experimental support in this embodiment is an iron frame, and a clamping mechanism is installed on the experimental support. The clamping structure is used to clamp the end of the petiole of the leaf. The clamping mechanism in this embodiment is a lower clamp 3. The liquid spraying mechanism includes an injection pump 4 and a needle-shaped nozzle 5. The injection pump 4 is connected to the needle-shaped nozzle 5. The needle-shaped nozzle 5 is fixed to the experimental support 1 through an upper clamp 11. A nozzle 6 is installed at the lower end of the needle-shaped nozzle 5, and the nozzle 6 is located just above the center of the leaf 7; a liquid storage device is provided in the injection pump 4, and the liquid storage device is used to store pesticides.

[0083] The piezoelectric ceramic 2 is annular and is installed outside the nozzle 6. The piezoelectric ceramic 2 is used to generate high-frequency vibration to stabilize the droplet injection. The piezoelectric ceramic 2 is connected to the high-frequency power amplifier 8, and the high-frequency power amplifier 8 is respectively connected to the arbitrary waveform generator 9 and the oscilloscope 10. The arbitrary waveform generator 9 is used to send a piezoelectric drive signal to the high-frequency power amplifier 8. The high-frequency power amplifier 8 is used to amplify the piezoelectric drive signal and drive the piezoelectric ceramic 2 to generate high-frequency vibration. The oscilloscope 10 is used to display the drive waveform signal amplified by the high-frequency power amplifier 8.

[0084] The camera is used to capture the process of pesticide droplets impacting the leaf surface; the image processing module is used to process the image obtained by the camera.

[0085] 5.2 Numerical measurement of blade vibration shape function, including the following steps:

[0086] (1) Install the upper clamp and the lower clamp on the iron frame, and use the lower clamp to clamp the end of the petiole of the Shucha Zaoxian leaf horizontally on the iron frame. Use the upper clamp to clamp the needle-shaped spray head, and the nozzle of the needle-shaped spray head is located directly above the Shucha Zaoxian leaf, so that the droplets sprayed from the nozzle hit the center of the Shucha Zaoxian leaf surface. Allow the Shucha Zaoxian leaf to deflect to the natural leaf inclination angle determined by the weight and stiffness of the leaf. In addition, keep the distance between the nozzle's water outlet and the Shucha Zaoxian leaf surface at 0.4m, which is the optimal distance between the backpack electric sprayer and the crop.

[0087] (2) Fix the high-speed camera on a tripod and use a standard lens to shoot the process of the droplets hitting the leaves of Shuchazao. Adjust the position of the tripod and keep the lens 0.4 m away from the target leaves to ensure that the high-speed camera can fully capture the process of the pesticide droplets falling.

[0088] (3) Adjust the focal length and aperture size of the lens, and surround the target with four tungsten halogen lamps to ensure that the camera has sufficient light intake, uniform lighting, and clear images under high-speed shooting; prepare the experimental solution. Pesticides are volatile, so the prepared solution should be stored in a sealed, low-temperature refrigerator.

[0089] (4) Figure 5 As shown, the syringe pump is connected to the needle nozzle, and the syringe pump is adjusted to the suction mode to suck the experimental liquid into the liquid reservoir of the syringe pump, and then switched to the injection mode to supply the liquid from the pressurized liquid reservoir to the needle nozzle at a constant flow rate. The injection velocity and droplet size are controlled by setting the volume flow of the syringe pump with nozzles of different apertures. During the falling process of the droplets, due to the drag force of the air, the droplets may coalesce or break. In order to reduce the influence of airflow disturbance on the accuracy of the experimental results, a transparent glass cover is used to separate the droplet generation area from the outside world during the experiment.

[0090] (5) Figure 5As shown, the arbitrary waveform generator is connected to the high-frequency power amplifier, the high-frequency power amplifier is connected to the oscilloscope and the piezoelectric ceramic, and the piezoelectric ceramic is set at the nozzle. The piezoelectric drive waveform is adjusted to a suitable value, and the piezoelectric drive signal is sent through the arbitrary waveform generator. After being amplified by the high-frequency power amplifier, the piezoelectric ceramic is driven to vibrate at a high frequency, so that the droplet injection is stable.

[0091] (6) The shooting speed of the high-speed camera is set to 4000 frames / second, and different working condition parameters are changed to capture the complete process from the occurrence of droplets to the impact on the leaf surface. Finally, the delay time of the five pesticide droplets continuously generated by the nozzle to the impact on the Shucha Zao leaf surface is measured by the computer post-processing system. The selection of the marker point is particularly critical for subsequent tracking and monitoring and the extraction of vibration parameters. The difficulty of extracting the marker point and the tracking effect of the marker point are important factors to be considered in the selection process of the marker point. The blade with one end fixed is simplified to a cantilever beam. Since the deflection at the end of the cantilever beam is the largest, the linear displacement perpendicular to the axis direction at the tip of the leaf after being hit by the droplet should be the largest. Therefore, it is easier for the computer to capture its displacement by taking the marker point at the tip of the leaf. In addition, the features at the tip of the leaf are the most obvious, and it is at the left end of the leaf edge curve, which is conducive to extracting and monitoring the marker point. In addition, this experiment was conducted indoors, meeting the three assumptions of the optical flow method: spatial consistency, small motion, and constant brightness. In summary, this embodiment decides to use the optical flow method and select the tip of the leaf as the marker point p for time domain displacement monitoring.

[0092] (7) The image processing technology can be used to track the marking points on the leaves of the Shuchazao in the image. The position of the marking points in each frame of the image can be recorded in the form of a list to obtain the time domain displacement curve of the marking points, such as Figure 6 As shown in the figure, the leaves of Shucha Zao vibrate after being hit by the mist droplets, and then the air damping and the clamp damping cause the oscillation to attenuate, that is, the amplitude of the leaves is in the form of attenuated oscillation.

[0093] Firstly, the dynamic response curve of the blade after being hit by droplets is extracted from the visual measurement results of the marked points under different working conditions, such as Figure 7 As shown, specifically, Figure 7 The curve is the curve of nozzle aperture 0.3mm and shooting speed 2m / s; secondly, the function model of the oscillation curve of Shucha Zao leaves after being hit by droplets is obtained by curve fitting technology Where y(t) is the displacement; Ae (-α*t) represents the amplitude of the change in the time domain, α is the attenuation coefficient, when α is greater than zero, it decays exponentially; ω represents the oscillation frequency; B represents the initial position, represents the initial angle, and t represents the time.

[0094] (8) The initial position of the marking point is considered to be 0, so B = 0. After curve fitting and optimization, the vibration shape function y(t) = Ae (-α*t) cos(ω*t), where A, ɑ, ω are parameters, and t is the actual time in the simulation. Its values ​​are shown in the following table:

[0095] Table 2 Parameter values ​​in the vibration mode function expressions under various working conditions

[0096]

[0097] 5.2 After obtaining the vibration shape function, in the multi-droplet impact simulation model based on the actual dynamic wall in step 4, edit the user-defined function (UDF), that is, the vibration shape function in step 4 (8), which is used to control the time, initial angle, initial speed and vibration of different pesticide droplets impacting the leaf surface.

[0098] 5.3 Edit the coordinates of different pesticide droplets in UDF. The height of subsequent pesticide droplets should be slightly higher. When the wall pesticide droplets are generated, they contact and hit the pesticide droplets. In this embodiment, the droplets are set to 5. If more droplets are needed, the batch input of droplet generation parameters can be realized through UDF programming. The five different droplet coordinates are (11.75, 5.1, -42), (11.9, 5.1, -42.15), (11.6, 5.4, -41.85), (11.6, 5.3, -42.15), (11.9, 5.3, -41.85). Since the innovation of this UDF is to generate corresponding droplets at different times, the height y of the droplets can be the same. It is only necessary to set the horizontal coordinates x and z to represent the different positions of the droplets. In the UDF, the droplet generation time of the corresponding coordinates is edited as droplet 1 0ms, droplet 2 and droplet 3 1ms, droplet 4 2.5ms, and droplet 5 4ms, so that droplets can be continuously generated at the corresponding time and coordinate position. In the UDF, the initial speed of the x, y, and z axes of the corresponding droplets can be set to indicate the impact angle of the droplets. In this embodiment, only the initial speed of the y axis is set to -2m / s. These functions are realized by accurately writing UDF code.

[0099] 5.3 Add and compile UDF in the Fluent user-defined part, and add user-defined function hooks. In this example, there are two UDFs: UDF for controlling the generation of pesticide droplets at different times and UDF for controlling leaf vibration. Figure 8 Part of the code shown.

[0100] 6. Numerical study of the dynamic behavior of multi-pesticide droplets impacting real leaf surfaces:

[0101] 6.1 Save the calculation results every 10 time steps. After the calculation is completed, export the results to Tecplot software to process and analyze the liquid phase spread. Fig. 9 As shown, spreading speed and leaf surface pressure.

[0102] 6.2 In the "Report Definition" option of ANSYS Fluent software solution, create a "Wall Report", select the blade wall and wall pressure, and measure the change of the wall pressure on the blade surface after the real blade surface is impacted by the droplets during the impact process; the software will automatically measure during the calculation process, save the data in the file, and then process the data in the file into Fig.10 The curve graph shows that after the droplets hit the wall, the pressure on the blade wall increases. The change of pressure value over time is a typical feature of the droplet impact process.

[0103] 6.3 In the "Report Definition" option in the solution, create a "Volume Report", select the droplet area and spatial velocity, and measure the change in the spreading speed of the droplets when they wet the leaf surface over time; the spreading speed of the pesticide droplets on the leaf surface after impact is a typical parameter that shows the wetting ability of the leaf. The change in spreading speed over time is affected by the pesticide droplet parameters, initial velocity and surface properties of the leaf, as well as the applied calculation method and model. The spreading speed shows the wetting ability of the leaf and also reflects the dynamic behavior changes of the pesticide droplets after impact, such as Fig.11 .

[0104] Compared with the traditional model building method that uses height difference instead of time difference, the results obtained by the method of this embodiment are not significantly different, which proves the effectiveness and feasibility of the model building method of this embodiment. Compared with the traditional model, when all calculation parameters are the same, this embodiment optimizes the generation form of droplets with UDF code, reduces the calculation domain of simulation, and shortens the calculation time.

[0105] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the structure of the present invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times, characterized in that: The following steps are involved: S1. Construct a three-dimensional multi-droplet static simulation model; S2, determine the best multi-pesticide droplet impact phase interface tracking method, surface tension model and grid establishment method; S3, optimize the grid and locally refine the pesticide droplet generation area; S4. Construct a multi-pesticide droplet impact simulation model based on actual dynamic wall; S5, editing a user-defined function to control the generation time, orientation and leaf vibration of multiple pesticide droplets, wherein the orientation includes the horizontal position, height and angle of impact of the pesticide droplets on the leaf surface; S6. Numerical study on the dynamic behavior changes of multi-pesticide droplet impact on real leaf surface to verify the feasibility of multi-pesticide droplet impact simulation model.

2. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 1, characterized in that: In step S1, the construction of the three-dimensional multi-droplet static simulation model specifically includes the following steps: S101, selecting the type of pesticide and measuring the physicochemical parameters of the pesticide required for numerical simulation; S102, setting the spatial dimension parameters, calculation boundary conditions and regional conditions of the simulation model; S103, setting droplet parameters in the simulation model.

3. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 2, characterized in that: In step S101, the physicochemical parameters of the pesticide include the surface tension, viscosity, and density of the pesticide droplets; In step S102, the boundary conditions are calculated including the initial temperature, operating pressure, and boundary inlet and outlet conditions of the entire calculation domain of the simulation model, and the regional conditions include the initial regional distribution of each phase; In step S103, the droplet parameters include size parameters and position parameters of the droplet.

4. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 1, characterized in that: In step S2, a continuous surface force and volume fraction coupling calculation model, a continuous surface stress and volume fraction coupling calculation model, and a continuous surface force and volume fraction corrected zero isosurface coupling calculation model are selected as a multi-pesticide droplet impact phase interface tracking method and surface tension model.

5. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 1, characterized in that: In step S2, three grid sizes are set: the overall calculation domain grid size, the leaf impact grid size, and the pesticide droplet generation area grid size.

6. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 1, characterized in that: In step S4, the construction of a multi-pesticide droplet impact simulation model based on an actual dynamic wall includes the following steps: S401, determining a real blade model; S402, establishing a three-dimensional calculation domain of the impact site; S403, setting impact simulation calculation boundary conditions according to the physical and chemical parameters of the real leaves and the pesticide spraying conditions.

7. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 1, characterized in that: Step S5 specifically includes the following steps: S501, setting a simulation device for pesticide droplets impacting leaf surfaces; S502, determining the initial position, initial velocity, and impact angle of the pesticide droplets; S503, measuring the vibration shape function of the leaf surface required for numerical simulation by simulating the impact of mist droplets on the leaf surface on the simulation device; S504. Standardize the editing of user-defined functions to ensure that the required functions are complete.

8. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 7, characterized in that: In step S501, the simulation device includes: An experimental stand, on which a clamping mechanism is installed, and the clamping structure is used to clamp the end of the petiole of the leaf blade; A liquid spraying mechanism, the liquid spraying mechanism comprises an injection pump and a needle-shaped nozzle, the injection pump is connected to the needle-shaped nozzle, a nozzle is installed at the lower end of the needle-shaped nozzle, and the nozzle is located just above the center of the blade; Piezoelectric ceramics, wherein the piezoelectric ceramic sleeve is installed at the nozzle, and the piezoelectric ceramics are used to generate high-frequency vibration to stabilize the spray droplet injection; A camera, which is used to capture the process of pesticide droplets hitting the leaf surface; An image processing module is used to process images obtained by a camera.

9. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 8, characterized in that: The piezoelectric ceramic is connected to a high-frequency power amplifier, and the high-frequency power amplifier is respectively connected to an arbitrary waveform generator and an oscilloscope. The arbitrary waveform generator is used to send a piezoelectric drive signal to the high-frequency power amplifier, and the high-frequency power amplifier is used to amplify the piezoelectric drive signal and drive the piezoelectric ceramic to vibrate at high frequency. The oscilloscope is used to display the drive waveform signal amplified by the high-frequency power amplifier.

10. The method for continuously impacting a leaf surface model with a pesticide droplet group at different positions and at different times according to claim 1, characterized in that: In step S6, the changes in dynamic behavior include the changes in the wall pressure on the real leaf surface after the pesticide droplets are impacted by the real vibrating leaf surface, the changes in the spreading speed of the droplets when wetting the leaf surface, and the changes in the droplet flow state at different times when the droplets fall and hit the leaves.

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