  Porous asphalt (PA) is an open-graded porous material with a porosity of 20%,
allowing fast drainage of rain and improving driving and acoustic conditions.
However, the high porosity leads to significant contact with water resulting in
a shorter life expectancy. To improve the durability and performance of PA, the
distribution of water and its residence time have to be understood which
entails capturing diverse multiphase phenomena. For these reasons, a numerical
study is performed to analyze in detail the fluid transport mechanisms at play
in PA, towards estimating the liquid distribution inside the nanometer- to
millimeter-sized pore structure of PA. In this study, LBM is used for a
detailed analysis of multiphase flow in complex porous domains. A multiphase
single component LBM method, with parallel computing, has been developed
different phase separation phenomena on surfaces and in porous media. The LBM
is validated with Laplace law and dynamic capillary intrusion test and then the
capillary uptake simulations are validated with analytical solutions, varying
contact angles, tube shapes and sizes. Pore meniscus and corner arc menisci are
studied in both square and triangular tubes. In order to address the behavior
of rain droplets on a PA surface, run-off, wetting, pinning and evaporation of
single droplet are considered in terms of effects of variation of contact
angle, surface wetting heterogeneity and structure. Finally, gravity-driven
drainage in PA is studied with LBM in accordance with temporal evolution of
water distribution by comparing with experimental data, showing good agreement.
This study allows a better understanding of the diverse multiphase flow
phenomena occurring in complex porous media, namely PA, at pore scale in
saturated and unsaturated states, providing information towards improving the
durability and performance of PA.
