| During the spray operation of plant protection UAV,the droplets are affected by air flow from formation to the settlement to the target.There are relatively stable space sections conducive to droplet settlement and enhanced pesticide application in the flow field.There are also turbulent areas with unstable flow lines and easy to create uneven droplets and drift.Therefore,accurately describing the flow field under the rotor,clarifying the velocity vector distribution of the different heights of the UAV rotor flow field,and simulating the detail of the flow field with high precision are the prerequisites for the accurate analysis of the sedimentation regularity of the droplet in downwash flow field under the rotor.In this study,the details of rotor flow field are numerically calculated based on CFD method,the purpose is to study the flow field characteristics of rotor flow field theoretically.Taking LTH-100 single rotor UAV as the research object,the flow field characteristics of UAV in hover state is numerically simulated,and the accuracy of numerical model is verified by wind speed distribution test.The rotor flow field of UAV in hover and forward flight under different lateral wind conditions are simulated and calculated.The influence of ambient air flow on the rotor flow field is analyzed,the wind speed distribution regularity at different heights of the rotor flow field is studies,the relationship model between the flow field space and the airflow velocity is establishes,which provides theoretical support for further theoretical analysis of the deposition regularity of droplets in the rotor flow field.Mainly reflected in the following aspects:(1)The hydrodynamic analysis of the rotor is carried out based on the blade element theory,and the relationship equation between the rotor motion parameters and the dynamic parameters of the rotor,such as the pull and torque,is established.Based on the CFD principle,this paper makes theoretical analysis on the numerical solution method of rotor flow field,clarifies the method of numerical calculation of rotor flow field,and preliminarily determines the relevant theoretical methods and general mathematical models used in each step of this simulation study.(2)A three-dimensional solid model of LTH-100 plant protection UAV is established.The rotor flow field of UAV is simulated based on CFD method,the rotor downwash flow field in hover state is simulated.This paper establishes an analysis mode to describe the characteristics of flow field in the direction of X,Y and Z axes in the three-dimensional coordinate system of flow field,analyzes the change of airflow velocity distribution in rotor flow field,determines the distribution trend of airflow velocity in flow field,analyzes the distribution regularity of airflow velocity in X,Y and Z direction in different height plane(3)The test platform of rotor flow field is established,the wind speed measurement experiment of rotor flow field is carried out by using the test platform,the accuracy of the simulated hover flow field is detected in practice.The test results show that the obtained measurement data can accurately characterize the wind speed of the flow field.The relative error analysis of the actual measured value and the simulated value is carried out,the average relative error of each measuring height and the average relative error mean of the measured data are investigated,the confidence level of the simulated data relative to the actual measured data is verified.(4)According to the principle of fluid mechanics and the actual simulation conditions,the numerical analysis method of rotor flow field with lateral wind interference is determined.The hover and forward flow field of UAV under different lateral wind conditions are numerically simulated.The influence of lateral wind on the velocity distribution of hover flow field is analyzed,and the coupling field of UAV rotor airflow-lateral wind is constructed,the distribution regularity of airflow velocity at different heights in the coupling field is analyzed.The prediction model between the spatial position and velocity of the flow field is established,and the confidence of the prediction model is tested by validation test. |
PDF Full Text Request