Experiments on convection in porous media

Solute transport and dispersion in underground geological formations play a key role in hydrology and geophysics, from carbon sequestration to water contamination. Understanding the underlying fluid dynamics is crucial to make reliable long-term predictions of the evolution of these systems. In this work, published on Physical Review Fluids and partially funded by the Austrian Science Fund (FWF), we investigate experimentally the role of convection on solute transport in confined porous media.

We assess experimentally the existence of a superlinear scaling for the growth of the mixing region in a confined porous medium. We employ an optical method to obtain high-resolution measurements of the density fields in Hele-Shaw flows, and we perform experiments for large values of the Rayleigh-Darcy number. We can confirm that the growth of the mixing length during the convection-dominated phase follows the scaling predicted by previous two-dimensional simulations. 

Thank you Diego Perissutti (visiting Master student at TU Wien at the time of the experiments, now PhD candidate at the University of Udine), Cristian Marchioli (University of Udine) and Alfredo Soldati (TU Wien and University of Udine) for the collaboration. This work has been partially performed at the University of Twente, Physics of Fluids Group.

In the movie, you can see the evolution of the finger number for one of the experiments considered.  Article, visualizations, and data about this work are available here:

[1] De Paoli et al., arXiv:2206.13363 (2022), https://arxiv.org/abs/2206.13363

[2] De Paoli et al., Phys. Rev. Fluids 7, 093503 (2022), https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.7.093503

[3] De Paoli et al., Data and figures in MatLab format, https://doi.org/10.6084/m9.figshare.19761766.v3

[4] Movie 1 https://youtu.be/njuebV7mLxw

[5] Movie 2 https://youtu.be/lC8Xbfal4J0

What is the flow topology of a convective porous media flow?

What is the minimum domain size we need to simulate to capture the large-scale flow structures?

We have addressed these questions in our recent work published on Journal of Fluid Mechanics. With the aid of massively parallelized numerical simulations, we show that the near-wall, large-scale temperature patterns (supercells) represent the footprint of the flow structure in the core of the domain (megaplumes). We have also analyzed the effect of the domain size (aspect ratio, AR), on the resulting flow topology.