Numerical modelling of flow field within a packed bed of granular material

Abstract

Computational domain discretization is the pre-processing stage in CFD analysis and it highly contributes to reducing the level of solution error as well as increasing the numerical stability of a model. The discretization of domain representing a packed bed of granular material is a demanding task due to the topology of the model consisting of spherical granules contacting tangentially and narrow regions in the direct vicinity of the contact point. Therefore the aim of the carried out research is to define guidelines to effectively discretize the computational domain representing the packed bed of granular material and validate it using Particle Image Velocimetry (PIV). Two methods of contact point representation between granules (contact point extension, granule radius reduction) and two mesh types (tetrahedral, polyhedral) are examined within the paper. Differences between the analyzed cases are discussed and compared to experimental research results. The obtained results prove that the applied method significantly affects the calculated porosity but does not affect the flow field considerably. Polyhedral mesh turned out to be preferable as the numerical model converges within substantially lower number of iterations and the obtained results are not as affected by the numerical diffusion as in the case of tetrahedral mesh.