Modelling a spray fan of a crop protection sprayer nozzle with the discrete element method

The testing of application equipment for crop protection products is very laborious due to the field trials usually required. For this reason, the use of simulation methods to reduce the required effort are desirable. To the knowledge of the authors, it has not yet been possible to develop a complete model of a crop protection nozzle and its spray fan. However, models already exist for certain sub-processes such as simulating the drift in computational fluid dynamics (CFD), though these are often not sufficiently validated. Suitable for a complete model is the discrete element method (DEM) i. e. due to the analogy between droplets and simulated particles and the simple contact detection during wetting. The first challenge is the recreation of the spray fan in the DEM, an approach to solve this issue is presented in this article. The simulation model generates a droplet spectrum 100 mm underneath the nozzle based on experiment data. For validation, the droplet spectrum and the transversal distribution are measured 500 mm underneath the nozzle. In the virtual environment the droplet spectrum shows high accordance in comparison to measurements whereas slight deviations in the transversal distribution exist.