Abstract：The particle flow in a vertical screw conveyor was simulated by the discrete element method. Periodic boundary conditions were proposed to solve the problem of computing efficiency in the vertical screw conveyor. Two simulation models of a full-sized model and a periodic model applied periodic boundary conditions were adopted. Flow characteristics of particles including particle movement form,normal contact force network,axial speed and its probability density distribution were obtained in the simulation. The periodicity of the conveyor was discussed in respect of the structure,particle movement form,normal contact force network and size and proportions of axial speed. The results show that simulated flow features in the two models with suitable periodic boundary conditions are consistent when the fill level is large and rotating speed is between 300 and 1 700 r/min. The proposed model with periodic boundary conditions can be generally used to investigate the granular flow in vertical screw conveyor in some case.

Keywords: vertical screw conveyor; periodic boundary condition; particle movement form; force network; axial speed