Numerical Investigation of Fluid Flow Through Glass Sphere Packed Bed Representative of High-Porosity Permeable Concrete

Permeable concrete allows rapid drainage of stormwater through otherwise impermeable infrastructure. Modelling the hydraulic performance of permeable concrete is challenging due to its tortuous pore structure. In this study a robust numerical model, validated against experimental results, is developed for permeable concrete structures at higher porosity using glass spheres (GS) of different diameters. Monosized GS along with polysized combinations are used to represent an idealised permeable concrete structure. The effect of the pore characteristics, including porosity and mean pore size, along with the hydraulic gradient (HG) on permeability and hydraulic tortuosity is determined. Discrete element method and computational fluid dynamics (CFD) are both used to generate the GS and simulate water flow through the packed bed, respectively. Permeability measurements are conducted using both falling head (FH) and constant head methods. The results demonstrate a strong agreement between the FH permeability values obtained through the resolved CFD simulations and the experimental data, without requiring any calibration of the CFD model. In summary, the present study offers a high-resolution, experimentally validated and physics-based approach to understanding the permeability and tortuosity of permeable concretes modelled as packed sphere beds. It eliminates reliance on empirical adjustments, provides new insights into the effect of the different HG and establishes a generalised permeability correlation applicable to a wide range of scenarios.