Discrete element modelling and experimental validation for the falling process of dry granular steps

This paper presents an experimental validation of discrete element method (DEM) simulation for falling process of dry granular steps. Three chute slopes were considered in the study. The corresponding physical experiments were carried out in our previous study. The DEM simulations matched well with the experimental results regarding the external flow characteristics such as flow regimes, surface profiles, final deposit angles, velocity profiles at the sidewall, receding upper granular surfaces and flow rates. Subsequently, the DEM simulations were used to explore the internal flow patterns of the granular collapse, including translational velocity profiles and angular velocity profiles inside the granular assembly. According to the DEM simulation results, a mixed velocity profile (an upper convex and lower concave profile) appears in the central part of the chute, whilst the velocity profile follows a sidewall-stabilized heap (SSH) rheology (a concave profile) near the sidewall. The chute inclination facilitates the transformation from the SSH rheology to the mixed velocity profile in a narrow channel. The DEM simulations not only verify the experimental observation but also enhance the understanding of flow patterns induced by the collapse of dry granular steps.