When you add milk to a cup of coffee you can efficiently mix the components by stirring with a spoon: the system is brought from a state of separation – where the coffee and the milk exist in separate domains – to uniformity – where the coffee and milk are indistinguishably blended. In porous media such as soil, rock or blood vessels in the human body, it is the complicated flow paths that dictate how efficient the mixing is. Since mixing can bring chemicals into contact, it subsequently determines how fast chemical reactions occur. Mixing therefore has consequences for a broad range of natural and industrial processes; from CO2 storage below the Earth’s crust to drug delivery in the human body. In multiphase flow – when two or more liquids or gases are flowing together through the pores – the flow will vary in a complex way both in time and space, and we hitherto know very little about how the mixing occurs under these circumstances. The goal of this project is to reveal the mechanisms behind, and to establish a physical explanation for how mixing occurs in multiphase flow through porous media. We will achieve this by an interdisciplinary approach which develops and combines novel numerical, experimental and theoretical methods.
Mixing is the operation by which a system is brought from segregation to uniformity. Solute mixing exerts an important influence on chemical reactions by bringing reactants in contact. It thus controls processes across a wide range of natural and industrial porous systems; spanning from CO2 sequestration in deep aquifers, to drug delivery in the human body. Recent work has shown that the mixing dynamics in porous media are chaotic, implying that fluid elements are elongated at an exponential rate, potentially changing reaction rates by orders of magnitude compared to the predictions of conventional models. However, despite its ubiquity, very little is currently known about solute mixing in multiphase flows, i.e. when two or more phases are flowing together in a porous medium. Only very recently have the numerical methods, experimental techniques and theories of related systems reached a level of maturation where a quantitative investigation of these processes is feasible.
In the project M4, I will develop a new theoretical framework for understanding and exploiting how multiphase flow controls mixing in porous media. To achieve this goal, I will develop numerical methods for highly accurate simulation of mixing in multiphase flows. With my collaborators, I will design and execute novel experiments imaging solute mixing in 3D porous media and microfluidic geometries. The output will include fundamental knowledge of how mixing occurs in a wide class of systems, open-source computational tools and novel microscale mixer designs.
M4 brings together world-leading, complementary expertise on its two key ingredients: multiphase flow and mixing in porous media. It involves partners from the Universities of Oslo and Rennes and SINTEF Digital, and is an interdisciplinary collaboration unifying theoretical, numerical and experimental approaches, building on nonlinear dynamics, fluid mechanics and computer science, with perspectives to the many applications of microfluidics.