Study on key issues in the modelling of maize seeds based on the multi-sphere method

The multi-sphere model is widely used for the modelling of maize seeds in discrete element simulations. In this paper, the multi-sphere models of seed particle built by different researchers are analysed by comparing the simulated results and experimental data in terms of the bulk density, angle of repose, and percentage passing. In addition, the effect of the mass error and moment of inertia error between seed particle model and single actual seed particle on group behaviour of seed particles is studied. Subsequently, the influence of multiple contacts on the dynamic behaviour and static behaviour of an assembly of seeds is investigated under different Young's modulus of seed particles. The results show that: a) the 12-sphere model of horse-tooth shaped seeds, the 10-sphere model of ellipsoidal cone seeds, the 9-sphere model of spheroid-shaped seeds and the seed population composed of the 12-sphere model of horse-tooth shaped seeds, the 28-sphere model of truncated triangular pyramid-shaped seeds, the 10-sphere model of ellipsoidal cone seeds and the 9-sphere model of spheroid-shaped seeds can meet the test requirements better; b) there are no significant effects of mass error and moment of inertia error between single seed particle model and single actual seed particle on group behaviour of seed particles; c) the multiple contacts issue has a little influence on the group behaviour of seed particles when the number of contacts is less than a certain value. However, when the number of contacts exceeds a certain value, the multiple contacts issue not only has a significant impact on the dynamic behaviour of an assembly of seeds, but also has a great impact on the static behaviour of an assembly of seeds.