Simulation On The Repose Angle Of Granular Materials Using Discrete Element Method

The granular material exists widely in nature and engineering application. Repose angle is one of the important physical properties of granular materials which is used to characterize the state of the material in the process of rotating drum. Many scholars have studied the repose angle, however, current results show that most of simulated objects are spherical particles, whereas in practice, the objects mainly are non-spherical particles. In addition, the size of rotating equipment is not equivalent to that in actual production. Therefore, further research is needed to make to find out that whether the results from the small rotary drum can be extend to the industrial scale rotary drum equipment.To solve the problems mentioned above, the DEM modeling and simulation of granular material movement process at different rotational speeds (2.87rpm-17.23rpm) are carried out according to actual size of the rotating process equipment and the actual size of the cylinder material particles in the present work. The parameters of each module are set in the EDEMTM. Experimental set-up is established to simulate the material movement in rotating process equipment. Image information of material movement is obtained through image acquisition device. The detection algorithm of dynamic repose angle of granular materials based on image processing technology is presented. Based on this detection algorithm, the simulation curves and physical experimental curves of repose angel were obtained. The correctness of the DEM simulation results is verified by the comparison of the material state image and the dynamic curve of repose angle.Based on the accurate DEM model, simulation of the particle system in rotating process equipment are set up in manufacturing environment under different experimental conditions. It is found that when the diameter of drum is fixed, there is an obvious upward trend of repose angle from (30.27°±1.50° to 34.03°±0.32°) with the increasing rotational speed; when the rotational speed is fixed, there is an obvious downward trend of repose angle (from 37.23°±2.49° to 28.64°±0.49 °) with the increasing of diameter of drum. Such conclusions are consistent with those have been found by other staffs in the research of small drum, and prove that the rules of repose angle in small drums can be applied to industrial scales drums in certain scope.