Numerical simulation and verification of rotor downwash flow field of plant protection UAV at different rotor speeds

Kun Chang; Shengde Chen; Meimei Wang; Xinyu Xue; Yubin Lan

doi:10.3389/fpls.2022.1087636

Numerical simulation and verification of rotor downwash flow field of plant protection UAV at different rotor speeds

Front Plant Sci. 2023 Jan 26:13:1087636. doi: 10.3389/fpls.2022.1087636. eCollection 2022.

Authors

Kun Chang^{1

2}, Shengde Chen^{1

2

3}, Meimei Wang⁴, Xinyu Xue⁵, Yubin Lan^{1

2

3

6}

Affiliations

¹ College of Electronic Engineering, College of Artificial Intelligence, South China Agricultural University, Guangzhou, China.
² National Center for International Collaboration Research on Precision Agricultural Aviation Pesticides Spraying Technology, South China Agricultural University, Guangzhou, China.
³ Guangdong Laboratory for Lingnan Modern Agriculture, South China Agricultural University, Guangzhou, China.
⁴ Department of Mechanical Engineering, Anyang Institute of Technology, Nanjing Institute of Agricultural Mechanization, Ministry of Agriculture and Rural Affairs, Nanjing, China.
⁵ Nanjing Institute of Agricultural Mechanization, Ministry of Agriculture and Rural Affairs, Nanjing, China.
⁶ Department of Biological and Agricultural Engineering, Texas A&M University, College Station, TX, United States.

Abstract

In aerial spraying of plant protection UAVs, the continuous reduction of pesticides is an objective process. Under the condition of constant flight state (speed and altitude), the change of pesticide loading will inevitably lead to the shift of lift force and rotor speed generated by UAV rotor rotation, which will change the distribution of the rotor flow field and affect the effect of aerial spraying operation of plant protection UAV. Therefore, the rotor speed of UAV is taken as the research object in this paper, and the adaptive refinement physical model based on the Lattice Boltzmann Method (LBM) is used to numerically simulate the rotor flow field of the quadrotor plant-protection UAV at different speeds. A high-speed particle image velocimeter (PIV) was used to obtain and verify the motion state of the droplets emitted from the fan nozzle in the rotor flow field at different speeds. The results show that, with the increase of rotor speed, the maximum velocity and vorticity of the wind field under the rotor increase gradually, the top wind speed can reach 13m/s, and the maximum vorticity can reach 589.64s ^-1. Moreover, the maximum velocity flow value is mainly concentrated within 1m below the rotor, and the maximum vorticity value is primarily concentrated within 0.5m. However, with the increase of time, the ultimate value of velocity and vorticity decreases due to the appearance of turbulence, and the distribution of velocity and vorticity are symmetrically distributed along the centre line of the fuselage, within the range of (-1m, 1m) in the X direction. It is consistent with the motion state of droplets under the action of the rotor downwash flow field obtained by PIV. The study results are expected to reveal and understand the change law of the rotor flow field of plant protection UAVs with the dynamic change of pesticide loading to provide a theoretical basis for the development of precise spraying operation mode of plant protection UAVs and improve the operation effect.

Keywords: dynamic load effect; lattice Boltzmann method (LBM); particle image of velocity (PIV); plant protection UAV; the numerical simulation.

Grants and funding

The study was funded by Laboratory of Lingnan Modern Agriculture Project(NT2021009), the National Natural Science Foundation of China (Grant No.31901411), the Basic and Applied Basic Research Foundation of Guangdong Province (2022A1515011535), The 111 Project (D18019), the science and technology planning project of Guangzhou (202201010642), the leading talents program of Guangdong Province (2016LJ06G689), Key-Area Research and Development Program of Guangdong Province(2019B020214003).