CN-117408174-B - Simulation method and system for flow of air flow and deposition of fog drops in crown layer

CN117408174BCN 117408174 BCN117408174 BCN 117408174BCN-117408174-B

Abstract

The invention discloses a simulation method and a system for flow and droplet deposition of air flow in a canopy, and relates to the technical field of canopy internal simulation, wherein the method comprises the steps of determining a rotation domain, a canopy domain, a calculation domain, a fluid grid model and a solid grid model; the method comprises the steps of setting requirements on a fluid grid model by using Fluent software, converting a solid grid model into a particle model by using LS-DYNA software, setting the number of simulation step sizes, the time represented by each step size and the simulation ending condition, repeatedly executing the simulation process until the simulation ending condition is met, and outputting simulation results of airflow flow and mist deposition in a crown layer. The invention realizes the simulation of the flow of air flow and the deposition of fog drops in the inner part of the crown layer.

Inventors

GUO QIWEI
FU YIQING
TANG YU
TAN ZHIPING
HUANG HUASHENG

Assignees

广东技术师范大学

Dates

Publication Date: 20260505
Application Date: 20230314

Claims (6)

1. A method of simulating airflow and droplet deposition inside a canopy, the method comprising: constructing an unmanned aerial vehicle rotor wing source model and a fruit tree canopy model; Determining a rotation domain of the unmanned aerial vehicle rotor according to the unmanned aerial vehicle rotor source model; Determining the canopy domain of the fruit tree according to the fruit tree canopy model; Determining a calculation domain according to the rotation domain and the canopy domain; Constructing a fluid geometric model according to the rotation domain, the canopy domain and the calculation domain; performing grid division on the fluid geometric model to obtain a fluid grid model; Using Fluent software to set the surfaces except the bottom surface in the computing domain as pressure outlets, setting the bottom surface as a wall, setting the rotating speed of a rotor wing of the unmanned aerial vehicle according to the carrying capacity of the unmanned aerial vehicle where the unmanned aerial vehicle rotor wing source model is located, setting the center and the direction of the rotating domain, establishing a discrete phase model of droplet motion, determining that a nozzle is positioned under the rotor wing of the unmanned aerial vehicle by 0.1-0.5 m, the half angle of injection is 10-90 degrees, the flow rate of injection is 0.005 kg/s-0.02 kg/s, the release time is 0-10 s, the hole width is 0.0005-0.001, determining that a turbulence model is SST k-omega, setting a solving method as double precision, and determining that an iterative mode is coupling iteration; Performing grid division on the canopy domain to obtain a solid grid model; Converting the region where the solid grid model is located into an SPH particle model by using LS-DYNA software, setting particle parameters, wherein the particle parameters comprise density, type and size, setting contact surfaces between particles in a solid domain and grids in a fluid domain, setting total number and generation rate of the particles, setting the generation mode of the particles to be a particle dynamic generation mode, designating the generation quantity of the particles to be the same as the number of the grids in a canopy domain during simulation, and setting coupling interfaces of a peripheral wall surface and the fluid grid model to be completely resolved; Setting the number of simulation step sizes, the time represented by each step size and the simulation ending condition; And repeatedly executing a simulation process until the simulation ending condition is met, and outputting simulation results of airflow flow and droplet deposition in the crown layer, wherein the simulation process comprises the steps of solving a fluid grid model result with a simulation step length in a Fluent environment, solving an SPH particle model result with a simulation step length in a LS-DYNA environment, and carrying out data exchange of the fluid grid model result and the solid grid model result through the coupling interface.
2. The simulation method for canopy internal airflow and droplet deposition according to claim 1, wherein the process for establishing the unmanned aerial vehicle rotor source model specifically comprises: Obtaining structural parameters of the unmanned aerial vehicle rotor wing, wherein the structural parameters comprise an outer diameter, a screw pitch, a thickness and an inclination angle; And establishing the unmanned aerial vehicle rotor wing source model according to the structural parameters.
3. The simulation method for the airflow flow and the mist deposition in the canopy of the fruit tree according to claim 1, wherein the establishment process of the canopy model of the fruit tree specifically comprises the following steps: The method comprises the steps of obtaining fruit tree parameters, wherein the fruit tree parameters comprise a lowest canopy point, a highest canopy point, an outer diameter of a canopy and a canopy density; and establishing the fruit tree canopy model according to the fruit tree parameters.
4. A simulation system of airflow and droplet deposition inside a canopy, the system comprising: The model building module is used for building an unmanned aerial vehicle rotor wing source model and a fruit tree canopy model; The rotation domain determining module is used for determining the rotation domain of the unmanned aerial vehicle rotor wing according to the unmanned aerial vehicle rotor wing source model; The canopy domain determining module is used for determining the canopy domain of the fruit tree according to the fruit tree canopy model; The calculation domain determining module is used for determining a calculation domain according to the rotation domain and the canopy domain; The fluid geometric model determining module is used for constructing a fluid geometric model according to the rotation domain, the canopy domain and the calculation domain; The fluid grid model determining module is used for carrying out grid division on the fluid geometric model to obtain a fluid grid model; The first setting module is used for setting the surfaces except the bottom surface in the computing domain as pressure outlets by utilizing Fluent software, setting the bottom surface as a wall, setting the rotating speed of the unmanned plane rotor wing according to the carrying capacity of the unmanned plane where the unmanned plane rotor wing source model is located, setting the center and the direction of the rotating domain, establishing a discrete phase model of fog drop movement, determining that the nozzle position is positioned under the unmanned plane rotor wing by 0.1-0.5 m, the half-angle of injection is 10-90 degrees, the flow rate of injection is 0.005 kg/s-0.02 kg/s, the release time is 0-10 s, the hole width is 0.0005-0.001, determining that the turbulence model is SST k-omega, setting the solving method as double precision, and determining that the iterative mode is coupling iteration; The solid grid model determining module is used for carrying out grid division on the canopy domain to obtain a solid grid model; The second setting module is used for converting the area where the solid grid model is located into an SPH particle model by utilizing LS-DYNA software, setting particle parameters, wherein the particle parameters comprise density, type and size, setting the contact surface between particles in the solid domain and grids in the fluid domain, setting the total number and the generation rate of the particles, setting the generation mode of the particles to be a particle dynamic generation mode, designating the generation amount of the particles to be the same as the number of grids in the canopy domain during simulation, and setting the coupling interface of the peripheral wall surface and the fluid grid model to be completely resolved; the third setting module is used for setting the number of simulation step sizes, the time represented by each step size and the simulation ending condition; The simulation module is used for repeatedly executing a simulation process until the simulation ending condition is met and outputting simulation results of airflow flow and mist deposition in the crown layer, wherein the simulation process comprises the steps of solving a fluid grid model result with a simulation step length in a Fluent environment, solving an SPH particle model result with a simulation step length in an LS-DYNA environment, and carrying out data exchange on the fluid grid model result and the solid grid model result through the coupling interface.
5. The simulation system of crown internal airflow and droplet deposition of claim 4, wherein the modeling module comprises an unmanned rotorcraft source modeling submodule, the unmanned rotorcraft source modeling submodule comprising: the structure parameter acquisition unit is used for acquiring structure parameters of the unmanned aerial vehicle rotor wing, wherein the structure parameters comprise an outer diameter, a screw pitch, a thickness and an inclination angle; and the unmanned aerial vehicle rotor wing source model building unit is used for building the unmanned aerial vehicle rotor wing source model according to the structural parameters.
6. The simulation system of canopy internal airflow and mist deposition of claim 4, wherein the modeling module comprises a fruit tree canopy modeling submodule, the fruit tree canopy modeling submodule specifically comprising: the fruit tree parameter acquisition unit is used for acquiring fruit tree parameters, wherein the fruit tree parameters comprise a lowest canopy point, a highest canopy point, an outer canopy diameter and canopy density; and the fruit tree canopy model building unit is used for building the fruit tree canopy model according to the fruit tree parameters.

Description

Simulation method and system for flow of air flow and deposition of fog drops in crown layer Technical Field The invention relates to the technical field of crown internal simulation, in particular to a simulation method and a simulation system for crown internal airflow flow and mist deposition. Background In the sustainable development process of agriculture, the problem of plant diseases and insect pests is always a focus of attention. The plant protection unmanned aerial vehicle is widely focused on the characteristics of flexibility, convenience and the like as an important tool for preventing and controlling plant diseases and insect pests, and has new progress in preventing and controlling plant diseases and insect pests. However, in the pesticide application process of the unmanned aerial vehicle, the effect of the crop canopy on the downward washing airflow of the rotor is not negligible, and the downward washing airflow wraps the fog drops to move, so that the space movement of the fog drops and the attachment and penetration of the fog drops in the canopy are affected. Therefore, the air flow and the rule thereof when the plant protection unmanned aerial vehicle applies the pesticide to the fruit trees are clarified, and become important basis for evaluating the deposition effect of the fog drops in the crown layer, so that the pesticide application efficiency of the unmanned aerial vehicle can be improved pertinently. The current method for simulating the flow law in the canopy by utilizing computational fluid dynamics (ComputationalFluidDynamics, CFD) comprises the following two steps of (1) constructing a virtual crop by using a porous medium. The method is to construct a virtual crop model through geometric modeling, divide a structural grid in the whole calculation domain, establish a virtual crop canopy according to the relative position of an actually measured unmanned aerial vehicle and crops in the structural grid, and then set the resistance of an input flow field in a porous medium area to the canopy through Fluent simulation, wherein main parameters are an inertial resistance coefficient and a viscous resistance coefficient. (2) porous media-static porosity similarity method. The method is characterized in that the crop population is abstracted into porous medium planes with different porosities layer by layer according to the inherent layering and ordering formed by the fractal characteristics of the morphological structure of the crop, and the crop population under the porosities can be approximately described by combining the planes with enough different optical porosities according to the height. And replaces different crops or different growth forms of the crops by setting different static porosities. And establishing unmanned aerial vehicle spray simulation calculation models under different static porosities in the CFD, and performing simulation calculation to obtain the space distribution condition of the fog drops under different porosities. Since the porous medium only adds an additional loss of momentum to the momentum equation, the porous medium's effect on turbulence is only approximate and can cause flow field distortion to some extent. The air flow speed, fog drop deposition and the like in the built virtual crops cannot be accurately measured, namely the turbulence distribution in the built virtual crops after the air flow passes through the crops in actual operation cannot be reflected, and the simulation effect of the static porosity similarity method has a certain gap from the actual operation, so that the actual situation cannot be simulated. Therefore, the accuracy of the prior art in simulating the flow of air flow and the deposition of mist drops inside the crown layer is low, so that the improvement effect is poor in pertinently improving the efficiency of unmanned aerial vehicle application. Disclosure of Invention The invention aims to provide a simulation method and a system for flow of air flow and mist deposition in a crown layer, which realize simulation of flow of air flow and mist deposition in the crown layer. In order to achieve the above object, the present invention provides the following solutions: A method of simulating airflow and droplet deposition inside a canopy, the method comprising: constructing an unmanned aerial vehicle rotor wing source model and a fruit tree canopy model; Determining a rotation domain of the unmanned aerial vehicle rotor according to the unmanned aerial vehicle rotor source model; Determining the canopy domain of the fruit tree according to the fruit tree canopy model; Determining a calculation domain according to the rotation domain and the canopy domain; Constructing a fluid geometric model according to the rotation domain, the canopy domain and the calculation domain; performing grid division on the fluid geometric model to obtain a fluid grid model; Using Fluent software to set the surfaces except the bottom surface