Funded PhD in Seismology and Fluid dynamics
A fully funded 4-year PhD project at the Dublin Institute for Advanced Studies.
Studying underground fluid-flow behaviours is relevant for a range of applications, such as understanding fluid movements in aquifers, volcanoes, geothermal injection, and microseismic experiments. Describing the fluid-flow regime is generally complex as it depends on a series of case-dependent parameters, including fluid properties (velocity, viscosity, and the presence of two or three phases) and fracture characteristics (geometry, roughness). However, it has important implications, as fluids can generate a variety of seismic responses, which are crucial for natural hazard assessment and monitoring.
Following pre-existing models, some seismic signals are widely used to locate fluid movements, and provide fracture sizes and fluid compositions. In particular, there are diverse models explaining how long-standing vibrations, such as resonances, are generated. Most of these models require either the presence of a resonating body, such as a fracture or a cavity, or the movement of fluids, or both. While all these models have pros and cons, they usually assume certain fluid-flow regimes, conditions and contributions. For example, fluid pressure variations could trigger Krauklis waves propagation on the fracture walls, leading to its resonance, but this occurs only for a range of fluid viscosities and fracture widths (i.e, thick-fracture regime). Fluids could also generate resonances themselves through periodic fluid-flow instabilities such as vortex shedding or Kelvin-Helmholtz instabilities.
Even though these models provide important estimates to interpret observations, many important assumptions and uncertainties remain about them. For this project, the student will first focus on modelling the fluid movements inside a fracture using existing software, considering a range of fluid properties and fracture characteristics. The modelling will involve an unstable fluid-flow regime at high Reynolds numbers, and the influence on the resulting flow of key characteristics will be evaluated: i) a simplified version of a realistic 3D fracture with different thicknesses, lengths, shapes and roughness; ii) fluid properties (e.g., fluid velocity and viscosity, multi-phase flow). Realistic fluid properties encountered at volcanoes, underground water flow and fluid injections will be considered. These results will then provide the complex fluid excitation to model the seismic response of the fracture via wave propagation modelling. Finally, the modelling results will be compared to real data acquired during passive seismic monitoring of water reservoirs and/or volcanoes.
The general goal is to better understand how fluid and fracture characteristics relate to observed seismic responses, and provide quantitative estimates to improve the interpretation of signals used for monitoring and natural hazard assessment purposes.
Duration: The PhD position is funded for 4 years
Send a PDF copy of their transcript of records, a CV and a cover letter including motivation for applying, research interests and experience and the names and contact of two academic references in one PDF file to Prof. Jean-Baptiste Tary at email@example.com.
For full consideration, application materials must be received by October 29, 2023. Applications will continue to be accepted after this until the position is filled. Selected candidates will then be contacted for an online interview.
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