What happens in the soil beneath our feet is not directly visible to us. Yet lots of processes happen there that are of major importance for things like plant growth and crop yield. Water flows, dissolved salts and nutrients flow with the water, and animals live beneath the surface too. All of this happens in the hollow spaces in the soil, which are “pores” since soil is a “porous medium”.

Various processes–like flow, transport, and deformation–take place in porous media. Our exhibit shows these processes using the example of arable soil. The soil is porous, which means it contains hollow spaces, through which rainwater can seep. But water can evaporate again too. In fact, in extremely dry conditions, soil can even change shape and crack. We usually see this when it hasn’t rained for a long time and the weather is very hot. 

Our exhibit

Our exhibit shows an arable landscape with a spinach plant that reacts to different weather situations: rain, moderate sunshine, and extreme heat. Click on the three weather icons to move between the different situations. You can see what happens within the soil and how it affects the surface and atmosphere when it rains or the sun dries out the soil. Animations reveal the invisible “porous media processes”, like waterflow, transport of dissolved salts, and soil deformation, which cannot be seen with the naked eye. Test your knowledge in a quiz and delve into the world of porous media!

Porous media research

The University of Stuttgart has a “collaborative research center” that explores flow, transport, and deformation processes in porous media: SFB 1313. These processes are not exclusive to soil–they occur in many other porous media systems, e.g., fuel cells and bones. So this basic research helps us gain a fundamental understanding of processes in porous media, which can then be applied to other uses at a later stage.

What do porous media have to do with evaporation and soil drying out? What role do they play in the development of fuel cells or our understanding of how osteoporosis should be treated?

Using the example of arable soil, our exhibit shows you why research questions in this field are important and relevant to society. An international, interdisciplinary team at the University of Stuttgart is investigating flow, transport, and deformation processes in porous media. The Collaborative Research Center (SFB) 1313 on “Interface-Driven Multi-Field Processes in Porous Media – Flow, Transport and Deformation” is funded by the German Research Foundation (DFG) and provides the framework for the research.

What are porous media?

Porous media are materials or structures that have hollow spaces–the “pores”. Almost all materials are porous. Examples include natural soil, paper, asphalt, and even parts of the human body, such as bones or skin.

Flow, transport, and deformation

• Flow: Porous media are never “empty”. There are always fluids (e.g., water or oil) and gases (air, water vapor, oxygen, hydrogen, etc.) in their pores. These fluids and gases are in motion, flowing from higher-pressure to lower-pressure locations.
• Transport: By flowing through the porous structures, fluids or gases can transport other substances, e.g., salt dissolved in water.
• Deformation: Porous media can change shape due to the forces exerted by fluids, gases, or external factors. This is referred to as deformation.

What exactly is SFB1313's research about?

Understanding how fluids spread and move in porous spaces is useful in a number of areas–from energy storage to climate prediction. Things get interesting wherever fluids come up against fluids or solids because interfaces have a significant effect on flow, transport, and deformation processes in porous media systems. The research team is chiefly interested in how the pores’ geometry affects these processes and what happens when cracks occur inside the porous space. Their work is supported by experiments, mathematical models, and simulations.

Our research questions are:

• How can we best describe processes such as evaporation of fluids from porous media and how does the interface between fluid and gas affect this exchange process?
• How do cracks spread in porous media and how do they affect flow and transport?
• What happens when substances dissolved in water precipitate and form a deposit? How does this change the porous space and what are the consequences in terms of flow and transport?