On the effect of flow regime and pore structure on the flow signatures in porous media

Abstract

In this study, lattice Boltzmann method (LBM) is utilised for three-dimensional simulation of fluid flow through two porous structures, consisting of grains with the same diameter: (i) a homogeneous porous domain, in which the grains are placed with a simple cubic packing configuration, and (ii) a randomly-packed porous domain. An ultra-fine mesh size is considered to perform the simulations in three orders of magnitude of Reynolds number (), covering laminar to turbulent flow regimes, and capture different flow signatures. Pore velocity fields are derived, and their sample probability density functions (PDF) are analyzed versus time to investigate the dynamics of the flow. The analysis of the PDFs clearly shows that stagnant zones play a significant role in the formation of the pore flow fields, manifested by multimodal PDFs, and the distribution of the velocities in porous media at various cannot be characterized by a single PDF model regardless of the pore structure. While the velocities at the stagnant regions and in the vicinity of the solid boundaries are primarily affected by the viscous forces and exhibit a power-law PDF at different , the velocities in the main (preferential) flow pathways away from the boundaries are shown to be influenced by the inertial forces, hence having an exponential PDF when is low. At high, however, depending on the tortuosity of the porous structure, the velocities may exhibit an exponential or even Laplace PDF.

Three-Dimensional Printing of Synthetic Core Plugs as an Alternative to Natural Core Plugs: Experimental and Numerical Study

“…The boundary conditions applied were bounce back (for the internal solid no-slip boundary) and periodical (for the external boundary). Numerical simulation of fluid flow in digital rocks using the LBM is described in detail in the references [11][12][13][14][15][16][17][18][19][20].…”

“…The LBM provides an accurate, high-throughput method for solving fluid flow problems in porous media with complex geometries, such as those generated via digital rock physics. LBM is widely used to model pore-scale flow in porous structures [11][12][13][14][15][16][17][18][19][20]. For a general introduction to the application of lattice Boltzmann theory in porous media, see [11].…”

Lattice Boltzmann Modelling of Fluid Flow through Porous Media: A Comparison between Pore-Structure and Representative Elementary Volume Methods

“…Their study compares the velocity fields and PDFs at different Reynolds numbers and pore structures. It also observes different types of recirculating flow structures in the stagnant zones and the main pathways and discusses their implications for transport phenomena in porous media [18]. Mahmoudi et al [19] used LBM to investigate pore-scale mechanisms of fluid flow through porous media.…”

Estimation of the aerodynamic tortuosity of woven/wire screens

“…Thus, (aerodynamic or hydraulic) tortuosity of a medium can be defined as the deviation from the straight pathline of a microscopic flow, which can be identified by the changes in length of streamlines [51,46]. Tortuosity is not a very popular term in fluid flow past screens, but it definitely is in general porous media literature [52,53,54,55,56], and of course in analogous electric conductance studies [45,46,57]. Whilst the constriction factor of woven screens has been explored in detail by the authors of the present paper (see our recent work in [17]), the accurate estimation of tortuosity of WS has been still unexplored.…”