Investigation of Effects of Downwash Airflow Field on Droplet Motion Characteristics of Small Plant Protection Unmanned Aerial Vehicles

ZHANG Zhihong, ZENG Ronghao, LAI Qinghui, YUAN Shuo, SHEN Siyu, YANG Le


In an effort to investigate the influence of downwash airflow field on droplet motion characteristics of small unmanned aerial vehicles (UAVs) and enhance pesticide application efficiency, small UAVs were utilized as the basis and the Navier-Stokes (N-S) equations, realizable k-ε model, and Semi-Implicit Method for Pressure-Linked Equations algorithm were employed to detailed numerical simulations of the downwash airflow field and droplet dispersion motion during the spray process were carried out. The primary research focus encompassed the analysis of velocity characteristics of the UAV downwash airflow, droplet deposition characteristics, and the impact of operating height on pesticide deposition. By comparing simulated values with measured values, it was confirmed that the relative error between the simulation and the experiment remained within 20%, thereby verifying the feasibility of the downwash airflow field numerical model. Further simulation analysis results indicated that, under the influence of the UAV spray platform, the downwash airflow field attained its peak velocity at a distance of 1 m from the rotor. With the increase in operating height, the droplets gradually dispersed and diffused. The droplets were primarily distributed in two “airflow introduction zones” and two “airflow export zones”, which contributed to further optimization of spraying effects and enhanced efficiency of pesticide utilization. In light of the analysis results, it was substantiated that when the UAV flight operation attitude was kept flush with the ground and the operating height was adjusted to 0.8~1.0m, pesticide deposition could be significantly increased, ultimately improving the pesticide application efficacy of plant protection UAVs. The research result verified the feasibility of the numerical model of downwash airflow field, and provided a reference for the study of the drift and deposition of target fog droplets based on small plant protection UAVs.

Keywords: small plant protection unmanned aerial vehicle, downwash airflow field, numerical simulation, droplet deposition


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ZHANG Dongyan, LAN Yubin, CHEN Liping, et al. Current status and future trends of agricultural aerial spraying technology in China [ J ]. Transactions of the Chinese Society for Agricultural Machinery, 2014,45( 10) : 53 -59. (in Chinese)

ZHENG Yongjun, CHEN Bingtai, LC Ilaotun, et al. Research progress of orchard plant protection mechanization technology and equipment in China [J] . Transactions of the CSAE,2020, 36(20) : 110 — 124. (in Chinese)

LAN Y B, CHEN S, BRADLEY К F. Current status and future trends of precision agricultural aviation technologies [ J ]. International Journal of Agricultural and Biological Engineering, 2017, 10(3) : 1 - 17.

ZHANG Haiyan, LAN Yubin, WEN Sheng, et al. Operational effects of unmanned helicopters for pesticide spraying in rice field [J] . Journal of South China Agricultural University ,2019 ,40( 1 ) ; 116 — 124. ( in Chinese)

BILANIN A J, TESKE M E, BARRY J W, et al. AGDISP: the aircraft spray dispersion model, code development and experimental validation [J] . Transactions of the ASAE, 1989, 32( 1 ) : 327 -334.

RAFFEL M, RICHARD H, EHRENFRIED K, et al. Recording and evaluation methods of PIV investigations on a helicopter rotor model [ J]. Experiments in Fluids, 2004, 36( 1 ) : 146 - 156.

KIRK I W, HOFFMANN W C. Operational factors influence spray drift and deposition from helicopters [R ]. ASAE Paper No. 02 - AA06, 2002.

ORCHARD R D,NEISESS J, MOUNTS J, et al. Evaluation of the bell 205a - 1 turbojet helicopter and spray system for forest application of insecticide [ R ]. Pacific Northwest Forest and Range Experiment Station, Forest Service, US Department of Agriculture, 1974.

W ANG Juan, LAN Yubin, YAO Weixiang, et al. Effects of working height of single-rotor unmanned aerial vehicle on drift and droplets deposition distribution of areca tree [J] . Transactions of the Chinese Society for Agricultural Machinery, 2019,50(7) ; 109 - 1 19. (in Chinese)

WEN Sheng, HAN Jie, LAN Yubin, et al. Influence of wing tip vortex on drift of single rotor plant protection unmanned aerial vehicle [J] . Transactions of the Chinese Society for Agricultural Machinery, 2018, 49(8) : 127 - 137,160. (in Chinese)

ZHANG Haiyan, LAN Yubin, WEN Sheng, et al. Research progress in rotor airflow model of plant protection UAV and droplet motion mechanism [ J ]. Transactions of the CSAE, 2020,36(22) ; 1 —12. (in Chinese)

ZHANG Jian, ZHANG Chao, CHEN Qing, et al. Effect of ambient wind speed on downwash airflow and droplet deposition for six-rotor UAV[J ]. Transactions of the Chinese Society for Agricultural Machinery, 2022,53(8) ;74 -81. (in Chinese)

WANG Ling, ZHANG Qi, HOU Qihang, et al. Vertical distribution law of six-rotor plant protection UAV based on multi¬feature parameters[ J ]. Transactions of the Chinese Society for Agricultural Machinery, 2022,53(2) : 75 -83. (in Chinese)

W ANG Ling. Research on low-attitude droplets deposition and technologyof variable spraying measurement and control system based on multi-rotor crop protection UAV[D]. Beijing: China Agricultural University, 2017. (in Chinese)

ZHANG Jing, HE Xiongkui, SONG Jianli, et al. Influence of spraying parameters of unmanned aircraft on droplets deposition [J] . Transactions of the Chinese Society for Agricultural Machinery, 2012,43( 12) ;94 -96. ( in Chinese)

ZANG Ying, HE Xin’gang, ZHOU Zhiyan, et al. Comprehensive evaluation method for lifting characteristics of electric multi-rotor UAV for plant protection [J] . Transactions of the CSAE, 2018,34( 14) ;69 -77. (in Chinese)

XIAO Wei. Direct numerical simulation of compressible gas-solid two-phase turbulent boundary layer and transverse jet [D]. Hangzhou: Zhejiang University, 2021. (in Chinese)


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