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:
Flow and transport in porous media are relevant for many geophysical, industrial, and biological applications, including carbon sequestration, glacial drainage, papermaking, transport across vascular walls, and bacteria motility. Predicting the evolution of these systems is difficult because of the interplay between different physical features, such as complex flow patterns, convection and reaction, and transformation of the porous matrix through deformation and phase change. In addition, flow and transport in porous media are governed by physical processes that span a wide range of length and time scales. Rapidly increasing computational power has recently enabled threedimensional, high-resolution and time-dependent simulations of these flows at both the pore-scale and the Darcy-scale, producing an entire branch of flourishing research into multiphase flow in porous media. Experimental progress has also been substantial, thanks to improved measurement techniques inboth 2D and 3D. Therefore, it is now useful to review the many studies on the subject to provide an overview of the current state of the art, and to put future research paths in perspective. This course will provide an overview of the most up-to-date modelling approaches, numerical simulations, and experimental methods used to study the dynamics and properties of porous media flows characterized by convection and deformation.
Schematic representation of CO2 dissolution in saline aquifers
Fundamentals of transport in porous media will be presented, including upscaling techniques, thermodynamics of two-phase mixtures, Lagrangian interpretations, fractional diffusion, non-locality and memory.
Time-dependent evolution of convection-driven flows in different configurations will be analyzed, with reference to geophysical and industrial applications and with particular attention to the dynamics and structures of convection, effect of porous media properties on convection and transition from 2D to 3D convection. An overview of experimental and numerical techniques for convective flows in porous media will be presented and reviewed.
Principles of the coupling between flow, transport, and deformation in porous media will be presented. The small-deformation limit and classical linear poroelasticity will be discussed in the context of subsurface flows. Large-deformation poromechanics will be discussed in the context of polymeric hydrogels (including swelling and drying phenomena), paper-pulp suspensions (including viscoelasticity and plasticity), and granular media (including friction and rearrangement). The implications of deformation for the dispersion and mixing of solutes will be considered. Two-phase flows will be considered, including capillary and wettability effects. Phase-field approaches will be introduced in the context of multiphase solidification problems (including ice, methane clathrates, and lava) and applied to the growth and migration of gas bubbles in soft porous media.
The course is addressed to graduate students and researchers in applied mathematics, physics and chemical/mechanical engineering. The advanced topics and the presentation of current progress in this very active field will also be of considerable interest to senior researchers and industrial practitioners having a strong interest in understanding the multiscale complex behavior of such multiphase flows.
Marco De Paoli 