Abstract
Dispersion is an important phenomenon in solute migration in porous media, which is closely affected by pore structure. Traditional advection-dispersion equation based on continuous porous media assumption ignores the complex pore structure of porous media and is hard to reflect the microscale mechanism of solute migration. Previous studies have reported the observation of the scale effect in dispersion between laboratory experiments and field monitoring. However, the mechanism of the dispersion scale effect has not been fully understood yet. The equivalent pore network model (EPNM) describes the complex pore structure of porous media by statistic parameters, which can be an effective method to study the microscopic mechanism of solute transport. In this study, simulations based on EPNMs are carried out to study the influence of pore structure on dispersion. Influences of pore structure parameters including standard deviation of pore radius, curvature number, and coordination number on dispersion are systematically investigated and discussed. Results show that the increase in the standard deviation of pore body radius, and the decrease in curvature number and coordination number leads to the increase in dispersion coefficient, which can be explained by the distribution of pore throat velocity. The scale effect of dispersion persists even in statistically homogeneous porous media. The change of dispersion coefficient with distance can be fitted by a power function. The results imply that the inhomogeneity of microscopic velocity distribution influences dispersion and its scale effect, which can help to understand the microscopic mechanism of solute transport and determine the parameters used in macroscale simulations.
Keywords: Dispersion, Scale effect, Pore structure, Equivalent pore network model (EPNM)
9th International Congress on Environmental Geotechnics (ICEG2023)
Contaminant Fate and Transport