Throughout the previous studies,none of them are involved in analysing the downwash flow effect on the control surface of the Flapping Wing Rotor(FWR).An overset CFD numerical model is built up and validated to study ...Throughout the previous studies,none of them are involved in analysing the downwash flow effect on the control surface of the Flapping Wing Rotor(FWR).An overset CFD numerical model is built up and validated to study the downwash flow’s effect on the stability of the FWR.After simulation,a cone like self-lock region which acts as the critical condition determining the stability of FWR is found.Only when the flow’s resultant velocity acting on the control surface lies in the stable region,the FWR can keep stable.The size of the cone like self-lock stable region can be enlarged by increasing the maximum feasible deflection angle constrained by mechanical design or enhancing the equivalent downwash flow velocity.Among all the simulated cases,when J=2.67(f=5 Hz,■=5 r/s),the largest average equivalent downwash flow velocities are found.On the other hand,the recovery torque could be enhanced due to the increase of the arm of the lateral force.According to these simulation results,a 43 g FWR model with two control surfaces and two stabilizers is then designed.A series of flight tests is then conducted to help confirm the conclusion of the mechanism research in this work.Overall,this study points out several strategies to increase the flight stability of the FWR and finally realizes the stable climb flight and mild descent flight of the FWR.展开更多
The downwash flow field of the multi-rotor unmanned aerial vehicle(UAV), formed by propellers during operation, has a significant influence on the deposition, drift and distribution of droplets as well as the spray wi...The downwash flow field of the multi-rotor unmanned aerial vehicle(UAV), formed by propellers during operation, has a significant influence on the deposition, drift and distribution of droplets as well as the spray width of the UAV for plant protection. To study the general characteristics of the distribution of the downwash airflow and simulate the static wind field of multi-rotor UAVs in hovering state, a 3 D full-size physical model of JF01-10 six-rotor plant protection UAV was constructed using Solid Works. The entire flow field surrounding the UAV and the rotation flow fields around the six rotors were established in UG software. The physical model and flow fields were meshed using unstructured tetrahedral elements in ANSYS software.Finally, the downwash flow field of UAV was simulated.With an increased hovering height, the ground effect was reduced and the minimum current velocity increased initially and then decreased. In addition, the spatial proportion of the turbulence occupied decreased. Furthermore, the appropriate operational hovering height for the JF01-10 is considered to be 3 m. These results can be applied to six-rotor plant protection UAVs employed in pesticide spraying and spray width detection.展开更多
In the plant protection spray operation of UAVs,the process of droplet from formation to sedimentation target is affected by airflow,easy to form uneven deposition.Accurately description of rotor downwash flow field,c...In the plant protection spray operation of UAVs,the process of droplet from formation to sedimentation target is affected by airflow,easy to form uneven deposition.Accurately description of rotor downwash flow field,clarification of velocity vector distribution at different heights of the UAV rotor flow field,simulation of the flow field with high precision,which are the prerequisites for accurately analyzing the droplet deposition distribution in rotor downwash flow field.Based on CFD method,the detail of rotor flow field was numerically calculated.Taking LTH-100 single-rotor agricultural UAV as the research object,the three-dimensional solid model of UAV was established,the Reynolds average N-S equation was used as the control equation and the RNGκ-εas the turbulence model to simulate the flow field of UAV in hover and lateral wind conditions,the wind velocity distribution at different altitudes of rotor downwash flow field was studied.The simulation results of the hover state showed that:In the flow field,the peak velocity appears in a circular distribution below the distal axis of the rotor.With the decrease of height,the peak velocity distribution area showed a tendency to expand gradually after small shrinkage;When the distance from the rotor was not more than 1.5 m,the downwash flow field presented an axisymmetric distribution based on the rotor axis,and the variation rate of velocity in the peak velocity was basically the same,turbulence in downwash flow field made the flow field more complex when the distance from rotor was larger than 2.0 m.On this basis,the optimal flight altitude of UAV is 1.5 m.Wind velocity test of the flow field was carried out on a rotor test bench,wind velocities at four altitudes of 0.5 m,1.0 m,1.5 m and 2.0 m were measured to verify the coincidence between the simulated and measured values.The test results showed that:the relative error between the measured and simulated values at four measurement heights were between 0.382-0.524,and the overall average relative errors was 0.430,which verified the confidence level of simulated values for measured values.When the lateral wind velocity was 3 m/s,4 m/s and 5 m/s,the simulation results showed that:The distribution trend of airflow velocity at the same altitude in lateral-wind flow field with different wind speeds was similar;When the lateral wind speed was 5 m/s,the coupling field formed by the lateral wind and rotor airflow cannot reach the height of 2 m below the rotor.The results of this study can provide more accurate environmental conditions for theoretical analysis of droplet deposition regularity in the flow field,and also provide methodological guidance for the related research on rotor flow field of multi-rotor UAV.展开更多
基金supported by the following funding organizations in China:National Natural Science Foundation of China(Grant No.52375116 and Grant No.52105285)the Aeronautical Science Foundation of China(Grant No.ASFC-20230023052001)+3 种基金China Postdoctoral Science Foundation(Grant No.2024M754237)National Key Research and Development Program of China(2024YFB470920001)Science and Technology Plan Project of Wenzhou Municipality(Grant No.ZG2024001)Basic Public Welfare Research Program of Wenzhou(Grant No.G2023046).
文摘Throughout the previous studies,none of them are involved in analysing the downwash flow effect on the control surface of the Flapping Wing Rotor(FWR).An overset CFD numerical model is built up and validated to study the downwash flow’s effect on the stability of the FWR.After simulation,a cone like self-lock region which acts as the critical condition determining the stability of FWR is found.Only when the flow’s resultant velocity acting on the control surface lies in the stable region,the FWR can keep stable.The size of the cone like self-lock stable region can be enlarged by increasing the maximum feasible deflection angle constrained by mechanical design or enhancing the equivalent downwash flow velocity.Among all the simulated cases,when J=2.67(f=5 Hz,■=5 r/s),the largest average equivalent downwash flow velocities are found.On the other hand,the recovery torque could be enhanced due to the increase of the arm of the lateral force.According to these simulation results,a 43 g FWR model with two control surfaces and two stabilizers is then designed.A series of flight tests is then conducted to help confirm the conclusion of the mechanism research in this work.Overall,this study points out several strategies to increase the flight stability of the FWR and finally realizes the stable climb flight and mild descent flight of the FWR.
基金supported and funded by The National Key Research and Development Program of China (2016YFD02 00700) from China Ministry of Science and TechnologyThe Fundamental Research Funds for the Central Universities (2015TC036 and 2017QC139)
文摘The downwash flow field of the multi-rotor unmanned aerial vehicle(UAV), formed by propellers during operation, has a significant influence on the deposition, drift and distribution of droplets as well as the spray width of the UAV for plant protection. To study the general characteristics of the distribution of the downwash airflow and simulate the static wind field of multi-rotor UAVs in hovering state, a 3 D full-size physical model of JF01-10 six-rotor plant protection UAV was constructed using Solid Works. The entire flow field surrounding the UAV and the rotation flow fields around the six rotors were established in UG software. The physical model and flow fields were meshed using unstructured tetrahedral elements in ANSYS software.Finally, the downwash flow field of UAV was simulated.With an increased hovering height, the ground effect was reduced and the minimum current velocity increased initially and then decreased. In addition, the spatial proportion of the turbulence occupied decreased. Furthermore, the appropriate operational hovering height for the JF01-10 is considered to be 3 m. These results can be applied to six-rotor plant protection UAVs employed in pesticide spraying and spray width detection.
基金This study was sponsored by Heilongjiang Province Conservation Tillage Technology Research CenterHainan Province Natural Science Foundation Program:Study on sedimentation mechanism of pesticide droplets in the chemical borer of sugarcane in single rotor UAV(Grant No.519MS097)+1 种基金Postgraduate research Innovation Project of Heilongjiang Bayi Agricultural University(Grant No.YJSCX2015-Z02)Innovation Team Project of Whole Mechanized Cultivation Techniques in Plant Bowl Breeding(Grant No.2014TD010).
文摘In the plant protection spray operation of UAVs,the process of droplet from formation to sedimentation target is affected by airflow,easy to form uneven deposition.Accurately description of rotor downwash flow field,clarification of velocity vector distribution at different heights of the UAV rotor flow field,simulation of the flow field with high precision,which are the prerequisites for accurately analyzing the droplet deposition distribution in rotor downwash flow field.Based on CFD method,the detail of rotor flow field was numerically calculated.Taking LTH-100 single-rotor agricultural UAV as the research object,the three-dimensional solid model of UAV was established,the Reynolds average N-S equation was used as the control equation and the RNGκ-εas the turbulence model to simulate the flow field of UAV in hover and lateral wind conditions,the wind velocity distribution at different altitudes of rotor downwash flow field was studied.The simulation results of the hover state showed that:In the flow field,the peak velocity appears in a circular distribution below the distal axis of the rotor.With the decrease of height,the peak velocity distribution area showed a tendency to expand gradually after small shrinkage;When the distance from the rotor was not more than 1.5 m,the downwash flow field presented an axisymmetric distribution based on the rotor axis,and the variation rate of velocity in the peak velocity was basically the same,turbulence in downwash flow field made the flow field more complex when the distance from rotor was larger than 2.0 m.On this basis,the optimal flight altitude of UAV is 1.5 m.Wind velocity test of the flow field was carried out on a rotor test bench,wind velocities at four altitudes of 0.5 m,1.0 m,1.5 m and 2.0 m were measured to verify the coincidence between the simulated and measured values.The test results showed that:the relative error between the measured and simulated values at four measurement heights were between 0.382-0.524,and the overall average relative errors was 0.430,which verified the confidence level of simulated values for measured values.When the lateral wind velocity was 3 m/s,4 m/s and 5 m/s,the simulation results showed that:The distribution trend of airflow velocity at the same altitude in lateral-wind flow field with different wind speeds was similar;When the lateral wind speed was 5 m/s,the coupling field formed by the lateral wind and rotor airflow cannot reach the height of 2 m below the rotor.The results of this study can provide more accurate environmental conditions for theoretical analysis of droplet deposition regularity in the flow field,and also provide methodological guidance for the related research on rotor flow field of multi-rotor UAV.
