"GRAIN-SCALE FLOW MODELING IN POROUS MEDIA USING HYBRID NUMERICAL METHODS"
Flow through porous media; Numerical Methods, Computational fluid dynamics; Virtual packings; Real particles
In the present work, grain-scale flow analyses in porous media are presented using hybrid numerical methods. Porous media made from virtual particles with realistic morphology are developed based on the characterization of real granular materials by digital image processing. After morphologically describing a large number of particles, a virtual repository is created with three-dimensional solids that statistically represent the shape of the real particles. The first of the numerical methods used is the algorithm for packing random particles from the repository that generates the virtual porous media. The algorithm is based on the discrete element method (DEM). The modeling of flow within the void matrix obtained from the virtual particle packings is then performed by a computational fluid dynamics (CFD) software. This eliminates the need to use a continuum approach for the porous medium. The methodology presented makes it possible to obtain the distributions of the characteristic flow variables throughout the porous matrix, rather than averaged values obtained for a representative elementary volume (REV). Six packings of virtual particles with different grain sizes were used, with dimensions varying between 4.8 and 32 mm. The results obtained here were then compared with the calculations from flow resistance models widespread in the literature, that were developed with the assumption of the porous medium as a continuous material. Furthermore, the numerical results were validated by experimental data obtained from laboratory tests using a hydraulic channel and real granular material used as a basis for assembling the virtual packings. The merge of numerical methods presented in this work proved to be quite effective, with great analytical value, with qualitative and quantitative advantages. The graphical features available in CFD modeling can be used as powerful tools for visualizing a complex phenomenon that occurs inside the pore network of geotechnical granular materials, represented virtually in an innovative realistic way.