Abstract：The discrete element method (DEM) was employed to simulate the motion and mixing of internal particle group composed of four different diameters acrylic particles in a mechanical high speed mixer. Analysis of the characteristics of particle mixing shows that the rapid mixing zone is mainly distributed in the middle and lower part of the mixer. Under the action of the agitator blade, the internal particles under a continuous spiral up and down condition. Besides, it forms a whirlpool in the center of the vessel. The high speed chopper prevents the particles from gathering together effectively. The special structure of high speed mixer and the flow behavior of different sizes particles lead to the phenomenon of small particle segregation occurs at the edge of the stationary process. The force and velocity of the particles decrease gradually with the increase of the height, and the decrease of particle force and velocity slow down with the increased height. The greater the particle size is, the higher particle force and velocity are. High-speed rotating particles are subjected to greater centrifugal force and it makes the normal force higher than the tangential force. The greater disparity between normal force and tangential force with the increase of particle size.

Keywords： mechanical high speed mixer; discrete element method; polydisperse particles; particle motion; particle force