Parallel Coupling of CFD-DEM simulations (original) (raw)

Dem-CFD Coupling : Mathematical Modelling and Case Studies Using Rocky-Dem ® and Ansys Fluent ®

2015

Coupling between Discrete Element Modelling (DEM) and Computational Fluid Dynamics (CFD) packages is a promising approach to model granular-fluid systems, enlarging the range of particle-fluid processes that can be managed with numerical simulation. In this paper, coupling approach for the commercial software packages Rocky® (DEM) and ANSYS Fluent® (CFD) will be addressed. Rocky® is a powerful DEM software that can handle true non-round particle shapes, breakage, physical wear and is efficient on both CPU and GPU systems, among other capabilities. ANSYS Fluent® package is well known as one of the world leaders for CFD applications. Mathematical modelling for DEM, CFD and the coupling itself will be described, as well as two case studies. The first one is a one-way coupling case, meaning that only the fluid flow affects the particle movement. This example demonstrates the method capability of considering the effect of drag force on the particles. Also, the importance of choosing a su...

An adaptive timestepping methodology for particle advance in coupled CFD-DEM simulations

arXiv: Computational Physics, 2018

An adpative integration technique for time advancement of particle motion in the context of coupled computational fluid dynamics (CFD) - discrete element method (DEM) simulations is presented in this work. CFD-DEM models provide an accurate description of multiphase physical systems where a granular phase exists in an underlying continuous medium. The time integration of the granular phase in these simulations present unique computational challenges due to large variations in time scales associated with particle collisions. The algorithm presented in this work uses a local time stepping approach to resolve collisional time scales for only a subset of particles that are in close proximity to potential collision partners, thereby resulting in substantial reduction of computational cost. This approach is observed to be 2-3X faster than traditional explicit methods for problems that involve both dense and dilute regions, while maintaining the same level of accuracy.

Extended CFD–DEM for free-surface flow with multi-size granules

Computational fluid dynamics and discrete element method (CFD–DEM) is extended with the volume of fluid (VOF) method to model free-surface flows. The fluid is described on coarse CFD grids by solving locally averaged Navier–Stokes equations, and particles are modelled individually in DEM. Fluid–particle interactions are achieved by exchanging information between DEM and CFD. An advection equation is ap- plied to solve the phase fraction of liquid, in the spirit of VOF, to capture the dynamics of free fluid surface. It also allows inter-phase volume replacements between the fluid and solid particles. Further, as the size ratio (SR) of fluid cell to particle diameter is limited (i.e. no less than 4) in coarse-grid CFD–DEM, a porous sphere method is adopted to permit a wider range of particle size without sacrificing the resolution of fluid grids. It makes use of more fluid cells to calculate local porosities. The developed solver (cfdemSolverVOF) is validated in different cases. A dam break case validates the CFD-component and VOF-component. Particle sedimentation tests validate the CFD–DEM interaction at various Reynolds numbers. Water-level rising tests validate the volume exchange among phases. The porous sphere model is validated in both static and dynamic situations. Sensitivity analyses show that the SR can be reduced to 1 using the porous sphere approach, with the accuracy of analyses maintained. This allows more details of the fluid phase to be revealed in the analyses and enhances the applicability of the proposed model to geotechnical problems, where a highly dynamic fluid velocity and a wide range of particle sizes are encountered.

A DEM-FEM Coupling Approach for the Direct Numerical Simulation of 3D Particulate Flows

Journal of Applied Mechanics, 2011

A computational approach is presented in this paper for the direct numerical simulation of 3D particulate flows. The given approach is based on the fictitious domain method, whereby the Discrete Element Method (DEM) and the Finite Element Method (FEM) are explicitly coupled for the numerical treatment of particle-fluid interactions. The particle properties are constitutively described by an adhesive viscoelastic model. To compute the hydrodynamic forces, a direct integration method is employed, where the fluid stresses are integrated over the particles’ surfaces. For the purpose of verifying the presented approach, computational results are shown and compared with those of the literature. Finally, the method is applied for the simulation of an agglomeration example.