Modelling and simulation of fruit drop tests by discrete element method

Apple is one of the most widely consumed fresh fruit in the world. Simulation of kinetics and physical aspects of fruit could be considered as an emerging technology in most of harvest and postharvest phases. Impact damage of fruit is a common phenomenon during handling and transportation, therefore, in this work, experimental and computational analysis of the free fall of apples was conducted. Discrete element method (DEM) simulations of a free fall drop test were performed for four different apple-shaped models. DEM simulations can lead to promising new insights in phenomena involved in particulate processes and discontinuous systems, in which the shape model used plays a key role. This work demonstrated that shape modelling in DEM simulation could be a potentially helpful tool for analysing collisions, and the behaviour and dynamics of particle–particle (apple–apple) and particle-surface (apple-surface) contacts. The computational time of DEM simulation increases when the complexity of apple shape increased. It was found in this work that an increase in the number of spheres in model apple increased the accuracy of the numerical results until a threshold number of spheres was reached. Exceeding that threshold resulted in a decrease in the accuracy of the model. A model of an apple consisting of 50 spheres in 5 sets predicted the end up locations of apples after free-fall with the least errors. It was therefore considered as the most appropriate method for modelling apples in DEM simulations.