A Multi-Purpose Open Source CFD-DEM Approach

In this paper we present a multi-purpose CFD-DEM framework to simulate coupled fluid-granular systems. The motion of the particles is resolved by means of the Discrete Element Method (DEM), and the Computational Fluid Dynamics (CFD) method is used to calculate the interstitial fluid flow. The focus of this paper is to show the ability of this coupled CFD-DEM framework to handle different scales and physical phenomena. Firstly, with “approach A” we show the applicability of the coupling framework for flows, where the particle sizes are significantly smaller than the CFD grid. The motion of an incompressible fluid phase in the presence of a secondary particulate phase is then governed by a modified set of Navier-Stokes-Equations accounting for the volume fraction á occupied by the fluid, and a momentum exchange term pf R. Secondly, with “approach B” we show the applicability of the coupling framework to the case of large particles and fine computational grids using the fictitious domain / immersed boundary method. In the first step the incompressible Navier-Stokes equations are solved over the whole domain. The next task is to correct the bodies’ velocities in the affected cells (i.e. those cells, which are covered by the immersed bodies). Finally a correction-operation is applied to account for the divergence-free condition of the flow field. Both approaches are successfully tested against analytics as well as experimental data. Application examples of the coupling are shown, ranging from to floatation and fluidised beds (approach A) to sedimentation (approach B). Concluding, we show the versatility and applicability of the open source CFD-DEM framework (CFDEM, 2011) which is based on the DEM code LIGGGHTS (LIGGGHTS, 2011) and the open source CFD toolbox OpenFOAM® (OpenCFD Ltd., 2009). LIGGGHTS and an initial release of the CFD-DEM coupling are available for public download.