DEM Analysis of Flow Characteristics of Non-spherical Particles

The flow characteristics of granular materials have attracted extensive attention, and the research focus has gradually expanded from spherical granular materials to irregular granular materials. Zeng et al. (Powder Technol 313:112–121, 2017) used the combined sphere method to construct rice-shaped particles, and also analyzed the pulsation behavior of granular materials during the flow process through the total contact force and velocity fluctuation. Govender et al. (Appl Math Comput 319:318–336, 2018) compared the flow process of polyhedral and spherical particles in hoppers, and found that the polyhedral shapes significantly affected the flow rate of granular materials. Besides, granular materials exhibit more unique mechanical behaviors under external driving force. Liu and Nagel (Nature 396:21–22, 1998) firstly proposed the phase transition mode of granular materials, which is achieved by applying external stresses and then transforming the granular materials from blockage to flow. Meanwhile, the external driving force changes the structural form of the granular material, leading to more strain intensification and expansion effects. In localized regions, the granular materials exhibit fluid-like properties and incomplete Taylor vortices (Huang et al. in Acta Geotech 10:389–397, 2014). In addition, numerical simulation of the mixing process of granular materials in a rotating drum is another important research to analyze the granular flow, and the mechanistic study of its mixing and segregation characteristics is beneficial for the application of granular materials in industrial production. Particle friction and rotational speed significantly affect the flow characteristics of particles inside the rotating drum, and the dynamic angle of repose of the granular material increased with the increase of friction coefficient and rotational speed (Chou et al. in Adv Powder Technol 27:1912–1921, 2016). The mixing behavior of polyhedral particles inside a two-dimensional rotating drum was simulated by the SIPHPM method, and the results showed that triangular, quadrilateral, and hexagonal particles had higher mixing degrees compared to spherical particles (Gui et al. in Powder Technol 314:140–147, 2017). Superquadric equations were used to construct ellipsoidal particles for investigating the effects of different aspect ratios on the mixing process of non-regular granular materials (You and Zhao in Powder Technol 331:179–191, 2018). The results showed that the main axis direction of particles with high aspect ratios was basically parallel to the flow direction of the particles.