Combining Microtomography, 3D Printing, and Numerical Simulations to Study Scale Effects on the Permeability of Porous Media

Abstract

The analysis of the geometry of porous media is an important aspect of modern soil sciences. This comes from the fact that not only experimental studies but also numerical simulations demand a considerable knowledge of the porous matrix involved. Subsequently, the combination of microtomography, three-dimensional (3D) printing, and numerical simulations is studied. The first step in this process is choosing an artificial model for the soil. In the present study, 3D cellular automata were chosen. Following that, pore-scale permeability numerical simulations were considered in such artificial porous media. To bring numerical simulations to real-world situations, artificial porous media were 3D printed. By means of the methodology hereby presented, it is possible to generate specific porous media to isolate and study a given phenomenon of interest. The printings were subjected to a metrological analysis, which revealed that, for all samples analyzed, more than 95% of the linear deviations between the print and the computational model were smaller than the resolution of the printer (0.3 mm). This validates the usage of 3D prints as valuable tools to build artificial porous media. The real permeabilities of the printed porous media were obtained by a permeability experiment. Finally, numerical and real permeability values were compared, and a scale analysis for this property was carried out. It was found that the numerical routines can be used to correctly estimate the real permeability of a given porous medium. For example, the shape of the pore space can be completely known by digitally analyzing the computational medium, and specific parameters (e.g., pore throat size, pore size distribution, hydraulic mean radius, tortuosity) can be explicitly related to its permeability. In contrast, other 3D printing techniques have to be considered. Printing in flexible materials, for example, could provide samples for consolidation analyses.