Mixing uniformity of irregular sand and gravel materials in a rotating drum with determination of contact model parameters

A reasonable choice of the physical and contact parameters directly affects the accuracy of the simulation results, particularly when the discrete element method (DEM) is used to study the particle motion or collision events. To investigate the mixing uniformity of irregular gravel and sand materials in the rotating drum, the physical properties of irregular particles were measured, and various experiments were devised to calibrate the contact parameters of particles. Based on the measured parameters, several typical irregular gravel particle models were established by DEM, and the numerical simulations of the mixing uniformity of gravel and sand materials in the rotating drum were also carried out. Aiming to analyze the significance of each factor, the gravel filling degree, the rotational speed of the drum, the number of lifters and the diameter of the drum were selected as the influencing factors, and three levels were established to carry out orthogonal experimental research on material mixing in the rotating drum. The extent of mixing was quantitatively characterized by the Lacey mixing index. According to orthogonal analysis, the rotational speed was the most significant factor that influenced mixing, with a confidence level of more than 95%, and the diameter of the drum was the least significant. Furthermore, the range analysis showed that the optimal combinations of the experimental conditions were a gravel filling degree of 10%, 40 rpm rotational speed of the drum, 12 lifters and a 200 mm diameter drum. (C) 2019 Elsevier B.V. All rights reserved.