A study on the modelling method of maize-seed particles based on the discrete element method

Abstract

To build a widely applicable modelling method for maize seed particles, nine major maize varieties in mainland China are analysed. According to the analysis, maize seed particles can be simplified into 5 shapes, i.e., horse-tooth shape, truncated triangular pyramid shape, ellipsoid cone shape, spheroid shape and irregular shape, and there is a certain functional relationship between the characteristic sizes of each shape of maize seeds. On this basis, the particle models of four shapes of seeds with different accuracy are built using the multi-sphere method. Meanwhile, artificial roughness values are used for evaluation of the filling accuracy of the multi-sphere model, and the calculation formula of the artificial roughness is given. An analysis of the multiple contacts in the multi-sphere model is also performed. Based on the above works, the feasibility of the modelling method of the maize seed proposed in this paper is verified by comparing the experimental and simulation results of bulk density, angle of repose and “self-flow screening”. These results show that, when the artificial roughness values of the horse-tooth seed model, the truncated triangular pyramid seed model and the ellipsoid cone seed model are approximately 0.7 or less than 0.7 and the number of filling spheres of the spheroid seed model is no less than 9, then the corresponding simulation results are close to the experimental results. In addition, by comparing the results of the Hertz-Mindlin (no-slip) contact model and the HM-new-restitution contact model, it is also proven that the multiple contacts have less impact on the movement of an assembly of the particle models of maize seeds proposed in this paper.