Distribution regularity of downwash airflow under rotors of agricultural UAV for plant protection

Xin Liu, Wei Zhang, Haiba Fu, Xiaoming Fu, Liqiang Qi

Abstract


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 RNG κ-ε as 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.
Keywords: aviation plant protection, downwash flow field, distribution regularity, numerical simulation, single-rotor UAV
DOI: 10.25165/j.ijabe.20211403.4036

Citation: Liu X, Zhang W, Fu H B, Fu X M, Qi L Q. Distribution regularity of downwash airflow under rotors of agricultural UAV for plant protection. Int J Agric & Biol Eng, 2021; 14(3): 46–57.

Full Text:

PDF

References


Zhang D Y, Lan Y B. Research progress and prospect of agricultural aviation application technology in China. Journal of Agricultural Machinery, 2014; 45(10): 53–59. (in Chinese)

He X K, Bonds J, Herbst A, Langenakens J. Recent development of unmanned aerial vehicle for plant protection in East Asia. Int J Agric & Biol Eng, 2017; 10(3): 18–30.

Chen H B, Lan Y B, Fritz B K, Hoffmann W C, Liu S B. Review of agricultural spraying technologies for plant protection using unmanned aerial vehicle (UAV). Int J Agric & Biol Eng, 2021; 14(1): 38–49.

Zhou Z Y, Luo X W, Lan Y B, Xue X Y. Technological innovation and development strategy of agricultural aviation plant protection industry in China. Journal of Agricultural Engineering, 2013; 29(24): 1–10. (in Chinese)

Lan Y B, Thomson S J, Huang Y, Hoffmann W C, Zhang H. Current status and future directions of precision aerial application for site-specific crop management in the USA. Computers and Electronics in Agriculture, 2010; 74(1): 34–38.

Xue X Y, Tu K, Qin W C, Lan Y B, Zhang H H. Drift and deposition of ultra-low altitude and low volume application in paddy field. Int J Agric & Biol Eng, 2014; 7(4): 23–28.

Yang S H, Zheng Y J, Liu X X. Research status and trends of downwash airflow of spray UAVs in agriculture. Int J Precis Agric Aviat, 2019; 2(1): 1–8.

Wen S, Lan Y B. Analysis and test of atomization characteristics of ultra-low capacity swirl nozzle for agricultural UAV. Journal of Agricultural Engineering, 2016; 32(20): 85–93. (in Chinese)

Cao H Y. Modern helicopter rotor aerodynamics. Beijing: Beijing University of Aeronautics and Astronautics Press, 2015. (in Chinese)

Xin Y, Li P, Chen R L. Free wake calculation of hover rotor in ground effect. Journal of Aeronautics, 2012; 33(12): 2161–2170.

Wang C L, He X K. Test of sedimentary distribution characteristics of plant protection UAV application droplets based on spatial mass balance method. Journal of Agricultural Engineering, 2016; 32(24): 89–97. (in Chinese)

Yao W X, Lan Y B, Wang J, Wen S, Wang G B, Chen S D. Distribution characteristics of droplet drift by aerial injection of AS350B3e helicopter. Journal of Agricultural Engineering, 2017; 33(22): 75–83. (in Chinese)

Zhang H Y, Lan Y B, Wen S, Xu T Y, Yu F H. Research progress on wind field model and droplet motion mechanism of UAV rotor. Journal of Agricultural Engineering, 2020; 36(22): 1–12. (in Chinese)

Yang Z L, Ge L Z, Qi L J, Cheng Y F, Wu Y L. Study on the effect of spin air flow on spray amplitude of plant protection UAV. Journal of Agricultural Machinery, 2018; 49(1): 116–122. (in Chinese)

Fu H B, Zhang W, Zhang P, Sun H T, Qi L Q, Li R. Effect of spraying mode on effective spray amplitude of multi rotor plant protection UAV in wind field. Research on Agricultural Mechanization, 2021; 43(8): 164–170. (in Chinese)

Sitaraman J, Potsdam M, Wissink A, Jayaraman B, Datta A, Mavriplis D. Rotor loads prediction using helios: a multisolver framework for rotorcraft aeromechanics analysis. Journal of Aircraft, 2013; 50(2): 478–493.

Yu Z W, Cao Y H. Numerical simulation of three-dimensional turbulent field of front swirling wing. Journal of Aeronautics and Astronautics, 2006; 32(7): 751–755. (in Chinese)

Cao S N. Numerical analysis and experimental study on droplet deposition distribution of single rotor UAV spray. Jiangsu University, 2019. (in Chinese)

Kim J W, Park S H, Yu Y H. Euler and Navier-Stokes simulations of helicopter rotor blade in forward flight using an overlapped grid solver. 19th AIAA Computational Fluid Dynamics, San Antonio, Texas, June 22-25, 2009. doi: 10.2514/6.2009-4268.

Sankaran V, Sitaraman J, Wissink A, Datta A, Jayaraman B, Potsdam M, et al. Application of the helios computational platform to rotorcraft flowfields. 48th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition, Orlando, Florida, Jan. 4-7, 2010. doi: 10.2514/6.2010-1230.

Bian Y L, Li J P, Wang P F, Liu H J, Yang X. Experimental study on flow field distribution characteristics and operational performance of single rotary wing UAV. Journal of Hebei Agricultural University, 2020; 43(3): 115–120, 129.

Sitaraman J, Potsdam M, Wissink A, Jayaraman B, Datta A, Mavriplis D. Rotor loads prediction using helios: a multisolver framework for rotorcraft aeromechanics analysis. Journal of Aircraft, 2013; 50(2): 478–493.

Guo Q W, Zhu Y Z, Tang Y, Hou C J, He Y, Zhuang J J, et al. CFD simulation and experimental verification of the spatial and temporal distributions of the downwash airflow of a quad-rotor agricultural UAV in hover. Computers and Electronics in Agriculture, 2020; 172: 105343.

Thomson S J, Huang Y B, Hanks J E, Martin D E, Smith L A. Improving flow response of a variable rate aerial application system by interactive refinement. Computers and Electronics in Agriculture, 2010; 73(1): 99–104.

Cui S B. Pressure distribution analysis of UAV fuselage based on CFD. Agricultural Equipment and Vehicle Engineering, 2019; 57(8): 69–73. (in Chinese)

Tang Q, Chen L P, Zhang R R, Zhang B, Yi T C, Xu W. Atomization characteristics of standard fan nozzles and air-induced nozzles under high speed airflow. Journal of Agricultural Engineering, 2016; 32(22): 121–128. (in Chinese)

Wang C J, Song L J, He X K, Wang Z C, Wang S L, Meng Y H. Effect of flight parameters of plant protection UAV on sedimentary distribution characteristics of application droplets. Journal of Agricultural Engineering, 2017; 33(23): 109–116. (in Chinese)

Tang Q, Zhang R R, Chen L P, Deng W, Xu M, Xu G, et al. Numerical simulation of the downwash flow field and droplet movement from an unmanned helicopter for crop spraying. Computers and Electronics in Agriculture, 2020; 174: 105468

Zhang P, Deng L, Lyu Q, He S L, Yi S L, Liu Y D, et al. Effects of citrus tree-shape and spraying height of small unmanned aerial vehicle on droplet distribution. Int J Agric & Biol Eng, 2016; 9(4): 45–52.

Wang C L, He X K, Jane, BONDS, Qi P, Yang Y, et al. Influence of downwash flow field on droplet deposition distribution characteristics of eight rotor plant protection UAV under different flight parameters. Smart Agriculture, 2020; 2(4): 124–136. (in Chinese)

Yang F B, Xue X Y, Zhang L, Sun Z. Numerical simulation and experimental verification on downwash air flow of six-rotor agricultural unmanned aerial vehicle in hover. Int J Agric & Biol Eng, 2017; 10(4): 41–53.

Zhang H, Qi L J, Wu Y L, Musiu E M., Cheng Z Z, Wang P. Numerical simulation of airflow field from a six-rotor plant protection drone using lattice Boltzmann method. Biosystems Engineering, 2020; 197: 336–351.

Xue X Y. Application of aeronautical administration technology and its effect on rice quality. Nanjing: Nanjing Agricultural University, 2013. (in Chinese)

Xu W B, Wang J F, Wen J L, Wang X Y. Simulation of near-ground flight flow field of large load plant protection unmanned helicopter. Journal of Jiangsu University, 2017; 38(6): 665–671. (in Chinese)

Wang C L, Zeng A J, He X K, Song J L, Herbst A, Gao W L. Spray drift characteristics test of unmanned aerial vehicle spray unit under wind tunnel conditions. Int J Agric & Biol Eng, 2020; 13(3): 13–21.

Yang F B, Xue X Y, Zhang L, Sun Z. Numerical simulation and experimental verification on downwash air flow of six-rotor agricultural unmanned aerial vehicle in hover. Int J Agric & Biol Eng, 2017; 10(4): 41–53.

Zheng Y J, Yang S H, Liu X X, Wang J, Tomas N, Jian C, et al. The computational fluid dynamic modeling of downwash flow field for a six-rotor UAV. Front. Agr. Sci. Eng., 2018; 5(2): 159–167.

Wu Y L, Qi L J, Cheng Z Z, Xiao Y, Yang Z L, Liu W W, et al. Testing method and anti-drift capability analysis of downwash airflow distribution characteristics of multi-rotor UAV in hover. ASABE Annual International Meeting, Boston, Massachusetts, July 7–10, 2019

Zhao Q J, Xu G H, Zhao J G. New hybrid method for predicting the flowfield of helicopter in hover and forward flight. AIAA Journal of Aircraft, 2006; 43(2): 372–380.

Wei P, Shi Y J, Xu G H. Coupled Euler-Lagrange numerical method for complex rotor flow field. Journal of Aeronautics, 2013; 34(7): 1538–1547. (in Chinese)

Wang L, Chen D, Zhang M C, Wang Y, Yao Z, Wang S M. CFD simulation of low-attitude droplets deposition characteristics for UAV based on multi-feature fusion. IFAC-PapersOnLine, 2018; 51(17): 648–653.

Zhang S C, Xue X Y, Sun Z, Zhou L X, Jin Y K. Downwash distribution of single-rotor unmanned agricultural helicopter on hovering state. Int J Agric & Biol Eng, 2017; 10(5): 14–24.

Xiahou B, Sun D Z, Song S R, Xue X Y, Dai Q F. Simulation and experimental research on droplet flow characteristics and deposition in airflow field. Int J Agric & Biol Eng, 2020; 13(6): 16–24.

Xu H Y, Ye Z Y, Wang G, Shi A M. Calculation of the front waterfall field of the rotor based on the unstructured nested mesh. Journal of Northwestern University of Technology, 2006; 24(6):763–767. (in Chinese)

Shi Q. Numerical analysis of wash flow field in small unmanned helicopter ultra flight. Journal of Irrigation and Drainage Engineering, 2015; 33(6): 521–525. (in Chinese)




Copyright (c) 2021 International Journal of Agricultural and Biological Engineering

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.

2023-2026 Copyright IJABE Editing and Publishing Office