Numerical analysis of downwash flow field from quad-rotor unmanned aerial vehicles

Agricultural drones, also known as Unmanned Aerial Vehicles(UAV), have attracted increasing attention because of their advantages of small size, convenient handling, and the ability to function without a runway, and they are particularly suitable for small farmlands in Asia, especially in China. The downwash flow field caused by the rotors of agricultural drone is one of main characteristics and affects the droplet deposition and drift law. Studying the distribution characteristics and development law of the downwash flow field is the basis for improving the application performance of spray technology applied on agricultural drones. With the development of computational fluid dynamics, agricultural aerial spray modeling has become an area of academic interest. In this study, the numerical simulation method was used to calculate the downwash flow field model of the quad-rotor UAV, to analyze its distribution characteristics and development law over time at different flight speeds. The accuracy of the numerical simulation was verified by field test. The simulation results show that the average velocities of airflow under1.6m from rotors at 2, 4 and6m/s are 2.33 m/s,1.90m/s and1.03m/s, respectively, which are high enough to disturb most of plant canopy and enhance the penetration rate of droplets. The flight velocity of drone has a significant effect on the downwash flow field. With the increase of the flight velocity, the wake of drones is gradually raised, and the concentration of wingtip vortices increases. When the flight velocity is increased to6m/s, the wingtip vortex velocity reaches3.3m/s, which has a strong entrainment effect on the droplets and greatly increases the risk of droplet drift. Keywords: quad-rotor UAV for plant protection, agricultural drones, downwash flow field, flight velocity DOI: 10.33440/j.ijpaa.20200304.138 Citation: Zhang H Y, Lan Y B, Shen N W, Wu J Y, Wang T, Han J, Wen S. Numerical analysis of downwash flow field from quad-rotor unmanned aerial vehicles. Int J Precis Agric Aviat, 2020; 3(4): 1–7.