Pretty Porous


If we examine different objects or materials from the “outside,” the porous structure they have in common is often not visible to us. We have to zoom into them with a microscope to be able to distinguish the solids and the void spaces between them. There are different scales on which porous media can be examined more closely.

There is a distinction between the micro and macro scale.

Micro scale: this is the insight view, i.e. a zoom into the porous medium. In this way, the porous structure and pore geometry as well as the distribution of the fluid and solid phases become visible. Problems that can be described on the microscale are very small.

Macro scale: the macro scale (also called Darcy scale or REV scale) uses averaged “views” by defining properties that correspond to micro-scale effects.

Macro scale and micro scale
Credits: University of Stuttgart / SFB 1313

Porous media research happens on different scales. They can be explained with the help of the example of “soils”. 

If we look at an earth pile under the microscope, we can see that the individual grains of earth lie on top of each other, next to each other or below each other. The grains build the porous structure. The grains are the “solids”, and the void space between the solids is the “pore space”. This pore space is permeable and liquids and gases can easily flow through it.

The micro scale can be digitally recreated. To that end, researchers create a model that corresponds to the reality. With this model different scenarios can now be carried out.