Numerical investigation on the role of discrete element method in combined LBM-IBM-DEM modelling

Particle collisions play a very important role in determining the fluid–particle multiphase flow, and thus it is crucial to treat the particle–particle interaction using a felicitous method in numerical simulations. A novel combined lattice Boltzmann method (LBM)–immersed boundary method (IBM)–discrete element method (DEM) scheme is presented in this study with its application to model the sedimentation of 2D circular particles in incompressible Newtonian flows. The hydrodynamic model of the incompressible Newtonian flow is based on the Bhatnagar–Gross–Krook LBM, and a momentum exchange-based IBM is adopted to calculate the fluid–solid interaction force. The kinematics and trajectory of the discrete particles are evaluated by DEM, in which the particle–particle interaction rules are governed by theoretical contact mechanics to enable the direct use of real particle properties. This eliminates the need of artificial parameters and also improves the reliability of the numerical results. By using a more accurate and physical description of particle interaction, a ‘safe zone’ or threshold is also no longer required. Case studies of single particle settling in a cavity, and two particles settling in a channel were carried out, the velocity characteristics of the particle during settling and near the bottom were examined. A numerical example of sedimentation involving 504 particles was finally presented to demonstrate the capability of the combined scheme.