Using X-ray computed tomography in hydrology: systems, resolutions, and limitations

A combination of advances in experimental techniques and mathematical analysis has made it possible to characterize phase distribution and pore geometry in porous media using non-destructive X-ray computed tomography (CT). We present qualitative and quantitative CT results for partially saturated media, obtained with different scanning systems and sample sizes, to illustrate advantages and limitations of these various systems, including topics of spatial resolution and contrast. In addition, we present examples of our most recent three-dimensional high-resolution images, for which it was possible to resolve individual pores and to delineate air–water interfacial contacts. This kind of resolution provides a novel opportunity to follow the dynamic flow behavior on the pore scale and to verify new theoretical and numerical modeling approaches.