SUMMARYThis paper presents essential numerical procedures in the context of the coupled lattice Boltzmann (LB) and discrete element (DE) solution strategy for the simulation of particle transport in turbulent fluid flows. Key computational issues involved are (1) the standard LB formulation for the solution of incompressible fluid flows, (2) the incorporation of large eddy simulation (LES)-based turbulence models in the LB equations for turbulent flows, (3) the computation of hydrodynamic interaction forces of the fluid and moving particles; and (4) the DE modelling of the interaction between solid particles. A complete list is provided for the conversion of relevant physical variables to lattice units to facilitate the understanding and implementation of the coupled methodology. Additional contributions made in this work include the application of the Smagorinsky turbulence model to moving particles and the proposal of a subcycling time integration scheme for the DE modelling to ensure an overall stable solution. A particle transport problem comprising 70 large particles and high Reynolds number (around 56 000) is provided to demonstrate the capability of the presented coupling strategy.

SUMMARYAn advancing front-based algorithm is proposed to constructively generate a random initial packing for disks with di erent radii within a 2D domain, which is often required in discrete element methods (DEM). Depending on whether the domain boundary is included in the initial front and how the front is formed, two di erent versions of the algorithm, termed the closed and open form, respectively, are presented. The open form version has an inherent linear complexity. The closed form can achieve the same complexity under a relatively weak condition. The generated packing is not a globally optimal arrangement but achieves a locally highest density from the algorithmic point of view. The performance of the algorithm is illustrated in several examples. The major beneÿt of this development is the significant reduction of CPU time required for the preparation of an initial discrete object conÿguration in DEM simulations. It is demonstrated that it takes only 3:77 s for the proposed algorithm to generate one million disks on a PC with a one 1 GHz processor.

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