Parallel Open Source Cfd-dem for Resolved Particle-fluid Interaction

In the following paper we present a parallelized resolved method for the simulation of the dynamics of immersed bodies within fluids. The algorithm uses the so called Fictitious Domain Method (FDM) and combines the Lagrangian Discrete Element Method (DEM) for the tracking of the bodies and a Computational Fluid Dynamics (CFD) method for the calculation of the flow and pressure field of the fluid phase. In a first step the CFD-calculation is carried out, disregarding the solid bodies. Afterwards, the velocity information from the bodies is included and the force, the fluid imposes onto the bodies, is calculated. The last step consists of a correction-operation which ensures the fulfilment of the conservation equation. Dynamic local mesh refinement is used in the area of the bodies in order to keep the number of fluid cells to a minimum. The CFD-DEM coupling is realized within the Open Source framework CFDEMcoupling (www.cfdem.com), where the DEM software LIGGGHTS (www.liggghts.com) is linked against an OpenFOAM®based CFD solver. While both LIGGGHTS and the CFD solver could already be used for parallel computations, only a recent improvement of the algorithm permits the fully parallel computation of resolved problems. This parallelization permits the treatment of large-scale problems. The enclosed validation and application examples show the dynamics of the flow around settling and rotating spheres as well as an investigation of the settling of spheres regarding the Boycott effect.