About the project
The flow of liquids and gases inside porous networks is a rather common process. It happens for example when rain falls on a soil: as the water moves in, it displaces air from the pores between the soil grains. It is also very important for many industrial and environmental applications related for example to the storage of CO2 inside depleted oil reservoirs and the remediation of contaminated soils.
In many of those fluid displacement processes, thin layers of liquid are left on the surface of the grains forming the porous network (for example, seemingly dry soils frequently have thin layers of water covering their grains). Those thin layers play a significant role: they can connect distant parts of the system. This effect brings some positive and negative consequences. The enhanced thin film connectivity is used by plants to obtain water and nutrients, but it also provides a pathway for the fast-spreading of pollutants inside the soils. It is very important to understand these effects and this is the primary goal of this project: to produce a physics-grounded explanation for the stability and transport properties of the thin liquid film network. This will be done via experiments, theoretical analysis, and numerical simulations.
Our experimental approach will be based on the use of custom-built transparent porous samples, where we can directly map the whole thin film network. This mapping is very useful and prior to our recent work, it had never been experimentally obtained. The ability to map the film network will serve as an input for a new theoretical investigation of the problem, based on solid concepts from network theory (graph theory). This approach, coupled with network simulations, will allow us to have a full understanding of the physics of the problem. This new understanding will allow us for example to propose physics-based numerical routines to better describe the transport of liquids and the spreading of pollutants inside soils.
Objectives
The objectives of this project are:
1) Experimental characterization and physics-grounded explanation for film flow phenomena in porous media.
- Test the role of system parameters such as viscosity and gravity in the stability of thin liquid films and their transport properties.
- Devise and apply image analysis algorithms to systematically map the full thin film network.
- Proof of concept: system parameters can be tailored to maximize film flow.
- Image 3D film flow by extension of currently used 3D optical scanning techniques.
2) Develop a numerical scheme for the modeling of film flow phenomena.
- Incorporate film flow into pore network models (PNM).
- Test the film flow PNM against a Lattice-Boltzmann model. Compare both against experiments.
3) Frame the problem of liquid transport through thin films under the light of network theory.
- Analytical calculation of secondary network effective permeability using an approach based on weighted graphs.
- Derivation of the optimal transport properties of the network.
Outcomes
This is primarily a basic science project: its major outcome is the production of new knowledge associated with fluid transport in porous media. The project also brings some important practical outcomes: the experimental techniques open the possibility of a new line of theoretical investigation in porous media film flows (network theory). This opening will help to redefine how simulation techniques can be improved by the incorporation of film flow effects. This brings consequences that go beyond the physics community, being also relevant for hydrologists, soil scientists, and civil engineers.
Background
[1] Moura M., Flekkøy E. G., Måløy K. J., Schäfer G. and Toussaint R., “Connectivity enhancement due to film flow in porous media,” Phys. Rev. Fluids 4, 094102 (2019).
[2] Moura M., Måløy K. J., Flekkøy E. G. and Toussaint R., “Verification of a dynamic scaling for the pair correlation function during the slow drainage of a porous medium,” Phys. Rev. Lett. 119, 154503 (2017).
[3] Moura M., Måløy K. J., Flekkøy E. G., and Toussaint R., “Intermittent dynamics of slow drainage experiments in porous media: Characterization under different boundary conditions,” Front. Phys. 7, 217 (2020).
[4] Måløy K. J., Furuberg F., Feder J. and Jøssang T., “Dynamics of slow drainage in porous media,” Phys. Rev. Lett. 68, 2161 (1992).
[5] Flekkøy E. G., Schmittbuhl J., Løvholt F., Oxaal U., Måløy K. J. and Aagaard P., “Flow paths in wetting unsaturated flow: Experiments and simulations,” Phys. Rev. E 65, 036312 (2002).
Financing
The Research Council of Norway, NFR Researcher Project for Young Talents. Project number: 102657101.
Cooperation
- PoreLab, The Njord Centre, University of Oslo, Norway.
- PoreLab, Norwegian University of Science and Technology, Norway.