Interference Analysis of an Heavy Lift Multirotor Drone Flow Field and Transported Spraying System

Drones in agriculture can be used for a variety of different task, aimed to increase farm crop yields and/or accurately monitor growth status, simultaneously decreasing time, labour and resources. While for some specific task a medium size drone can be used, on the other hand for more intensive task like for example precision spraying of pesticide or fertilizer, an heavy lift drone is more appropriate. A growing momentum application consists in the possibility to use heavy lift drones for precision pesticide distribution. A report by the Association for Unmanned Vehicle Systems International (AUVSI) found that so-called "precision agriculture" will make up about 80% of the United States UAS market. Some of the multirotor already on the market are designed to spray large areas of farmland with pesticides or fertilizers, covering an extraordinary amount of distance quickly – 4,000-6,000 m² in just 10 minutes and reducing the amount of pesticide from 20% to 40%, with no exposure to risk for human being. The optimal design of transported spraying equipment requires a careful study of fluid dynamics interactions of the downwash wakes generated from the rotors and the spraying nozzle of horizontal or vertical bars. Experimental setups finalised to drones spraying analysis are complex to use, and the final results are strongly influenced by the operative and environmental conditions. A powerful tool for a preliminary investigation of such interactions is provided by computational fluid dynamics, allowing a predictive analysis of possible wash down wake effects with spraying operative setup. And in this work a CFD analysis of two different configurations (X6 and Y6 multirotors) is presented. The knowledge of aerodynamic effects will allow the optimisation of boom position and a correct setup of the discharge rate of chemical liquid according to the flying speed of the UAV.