  Properties of fluids flow in granular aggregates are important for the design
of pervious infrastructures used to alleviate urban water-logging problems.
Here in this work, five groups of aggregates packing with similar average
porosities but varying particle sizes were scanned by a high-energy X-ray
computed tomography (X-CT) facility. The structures of the packings were
reconstructed. Porosities were calculated and compared with those measured by
the volume and mass of infilled water in the packing. Then pore networks were
extracted and analyzed. Simulations of fluids flow in the packings were
performed by using a lattice Boltzmann method (LBM) with BGK
(Bhatnagar-Gross-Krook) collision model in the pore-network domain of the
packings. Results showed wall effect on the porosity of aggregates packing was
significant and the influence increased with the aggregate sizes. In addition,
Poisson law and power law can be used to fit the coordination number and
coordination volume of the packing's pore network, respectively. Moreover, the
mass flow rates of fluids in the aggregates were affected by the porosities. On
the two-dimensional slices, the mass flow rate decreased when the slice
porosity increased. But for the three-dimensional blocks, the average mass flow
rate increased with the volume porosity. And the permeability of the aggregates
packing showed correlating change trend with the average pore diameter and
fitting parameters of coordination volumes, when the sizes of aggregates
changed. Though the limitation of merging interfaces causing fluctuation and
discontinuity on micro parameters of fluid flow existed, the methods and
results here may provide knowledge and insights for numerical simulations and
optimal design of aggregate-based materials.
