Are you a UiO or NTNU student interested in writing your MSc thesis with me and collaborators? See below for a list of suggested projects. Do not hesitate to contact me!
Numerical simulation of mixing in microscale multiphase flow
Contact: Gaute Linga (gaute.linga at mn.uio.no)
Motivation: Solute mixing in porous media is essential to a host of industrial and natural processes, as it dictates the speed of chemical reactions by bringing reactants into contact. The mixing dynamics of steady single-phase flows through porous media are becoming well understood. However, for multiphase flows, e.g. when air and water flows together, very little is known. This partly stems from the fact that it is difficult to numerically resolve flows with strong capillary forces and low solute diffusion.
Project description: In this project, we will couple immiscible two-phase flow with solute transport. We will use a phase-field model to represent the interface between the two immiscible fluids and a diffusive strip method to resolve the solute transport. The MSc project will be tailored to the recruited student, but could include:
- Implementing and comparing different discretization schemes for the 3D fluid flow model. This will allow us to answer under which conditions (fully or partially) implicit schemes, with fewer but larger time steps, are advantageous over more explicit schemes, with more but smaller time steps.
- Investigate how mixing is influenced by two-phase flow in 3D periodic porous geometries.
- Numerically and theoretically investigate the role of advection versus solute diffusion for mixing and reactions in time-dependent flows.
Resources: The student will learn how to use HPC infrastructure and have access to Sigma2 and the PoreLab UiO/NTNU cluster. The project will benefit from comparison to experiments carried out under similar conditions (see other project).
Required background: Strong interest and basic skills in numerical methods, scientific computing, fluid mechanics. Some knowledge of statistical mechanics is an advantage.
Modelling pollutant spreading through capillary bridge networks in soils
Contacts: Paula Reis (paularei at uio.no), Marcel Moura (Marcel.Moura at fys.uio.no), Gaute Linga (gaute.linga at mn.uio.no)
Motivation: When water-saturated granular soils are drained or dried, water in the pore space between grains is replaced by air. This process leaves behind water clusters and bridges which are held in place by capillary forces [1]. These clusters and bridges can together form large-scale connected networks which may act as highways for pollutants or chemical solutes spreading in soils. However, how fast and how far solutes may spread in these networks, under different physical conditions, remains elusive. A better understanding of this process would be of immediate interest e.g. in the context of environmental remediation.
Project description: In this project, students will develop a numerical pore-network model that incorporates fluid and solute transport in arbitrary capillary bridge networks. We will effectively model flow and solute transport in individual bridges of the network by direct pore-scale simulation in representative geometries. Students will investigate how network structure influences the speed and extent of solute spreading, and characterise and/or theoretically describe the macroscopic behaviour, allowing us to predict critical conditions for pollutant spreading. The candidate will benefit from direct comparison with ongoing experiments at PoreLab UiO (see also the related experimental project).
Resources: Students will learn how to use national high-performance computing resources (Sigma2), and will have access to Sigma2 as well as the computing clusters of their unit (PoreLab UiO/NTNU).
Required background: Basic programming skills (Python, MATLAB and/or C++) and basic knowledge of fluid mechanics.
The role of pore fluid phase transition during earthquake ruptures: Insights from an idealised numerical model
Contact: Fabian Barras (fabian.barras at mn.uio.no), Eirik G. Flekkøy (e.g.flekkoy at fys.uio.no), Gaute Linga (gaute.linga at mn.uio.no)
Motivation: Earthquakes lead to large and fast changes in porosity along the fault and in the surrounding rock. Under water-saturated conditions, this rapid expansion of fluid-filled cavities and fractures could lead to transient phenomena such as vaporisation due to the resulting large pressure drop, impacting the propagating earthquake rupture. However, a proper quantification of the conditions leading to such events and their resulting stresses is needed.
Project description: In this project we propose to investigate the physics of a rapidly expanding fluid-filled cavity. The student will employ and develop a numerical model that fully couples solid and fluid dynamics at the tip of a rapidly growing tensile fracture. We will initially consider a single fluid-filled crack propagating between two semi-infinite solid blocks (see Figure). The compressible fluid dynamics within the expanding cavity will be simulated using a finite element method formulated on a moving mesh. The implementation of the fluid dynamic model will be validated against theoretical predictions. Next, the model will be used to identify the conditions leading to phase transition of the pore fluid and its impact on the surrounding solid, i.e. the formation and eventual collapse of cavitation bubbles. Throughout the project, the candidate will benefit from direct comparison with ongoing experiments at PoreLab UiO investigating cavitation in an analogue setup.
Resources: The candidate will learn how to use High-Performance Computing (HPC) infrastructure and will have access to the computing clusters of the Norwegian HPC infrastructure (Sigma2) as well as the local cluster of PoreLab UiO/NTNU.
Required background: Basic programming skills (C++, Python) and basic background in fluid mechanics. Some knowledge of solid mechanics and thermodynamics is an advantage.
Experimental imaging of chemical transport and mixing in multiphase porous media flows
Contacts: Kevin Pierce (j.k.pierce at mn.uio.no), Marcel Moura (marcel.moura at fys.uio.no), Knut Jørgen Måløy (k.j.maloy at fys.uio.no), Gaute Linga (gaute.linga at mn.uio.no)
Motivation: Solute mixing in porous media is essential to a host of industrial and natural processes, as it dictates the speed of chemical reactions by bringing reactants into contact. The mixing dynamics of steady single-phase flows through porous media are becoming well understood. However, for multiphase flows, e.g. when air and water flow together below Earth’s surface, very little is known, despite the prevalence of these flows in the environment.
Project description: We will employ state-of-the-art fluorescence imaging and stereolithography 3D printing techniques to study the dynamics of mixing in porous media. Our setup resolves the concentrations of initially-segregated chemicals in porous media flows through space and time. Image analysis techniques will be developed to analyse the mixing dynamics, and we will assess how different boundary and flow conditions affect the results. Experiments will be compared to numerical simulations performed under similar conditions. This project will provide insights into the fundamental physics underpinning applications from carbon dioxide sequestration to groundwater remediation.
Resources: The student will learn to use the fluorescence imaging and 3D printing facilities at PoreLab UiO and will have access to dedicated computing resources for image analysis.
Required background: Interest in fluid dynamics, experimental methods, and data analysis. Students with diverse backgrounds are especially encouraged to apply.
Experimental resolution of local flow velocities in multiphase flow through porous media
Contacts: Kevin Pierce (j.k.pierce at mn.uio.no), Marcel Moura (marcel.moura at fys.uio.no), Knut Jørgen Måløy (k.j.maloy at fys.uio.no), Gaute Linga (gaute.linga at mn.uio.no)
Motivation: Simultaneous flow of gases and liquids is ubiquitous in Earth’s porous subsurface, and governs biogeochemical processes ranging from contaminant degradation in groundwater to nutrient cycling in soils. While the velocities of single-phase flows through porous media are relatively well-understood, our understanding of the local flow velocities in multiphase flows remains limited. Partly, this is due to the challenge of measuring flow velocities simultaneously with the moving interfaces between different fluids.
Project description: The student will innovate new methods to resolve the local flow velocities and interface dynamics in flows through porous media, using the state-of-the-art imaging and 3D printing facilities at the PoreLab UiO laboratories. Multiphase flows through 3D-printed transparent models will be seeded with microscopic fluorescent tracer particles, and these particles will be tracked in high-speed videos to resolve real-time velocity fields in porous media. Flow characteristics will be quantified for different multiphase flow geometries (i.e., drainage, imbibition) and physical conditions (i.e., interfacial tensions and applied pressure gradients).
Resources: The student will have access to the laboratory facilities and experimental expertise at PoreLab UiO to construct particle-tracking velocity experiments. Students will benefit from direct comparison with simulations in identical geometries (see also the related computational project). Dedicated computing resources will be made available for image analysis.
Required background: Interest in fluid dynamics, experimental methods, and data analysis. Students with diverse backgrounds are especially encouraged to apply.
References:
- [1] P. Reis, M. Moura, G. Linga, P. A. Rikvold, E. G. Flekkøy, K. J. Måløy, A simplified pore-scale model for slow drainage including film-flow effects, Advances in Water Resources 182, 104580 (2023)