Description of the thesis topic

The physical phenomena involved both in the dynamics of granular flow in water and in the generation of elastic and hydro-acoustic waves are complex. This is why the starting point for this thesis will be “model” experiments on a laboratory scale, so that we can control the environment and vary the initial and boundary conditions as well as the parameters involved. To make the best use of these experiments, we will also carry out simulations using the discrete element method (DEM) interfaced with computational fluid dynamics (CFD) methods.
More specifically, the aim will be to develop an experimental approach to study the generation of elastic waves (equivalent to seismic waves) and hydro-acoustic waves during granular flows immersed in a tank approximately 2 metres long. The first part of the thesis will involve adapting the device we have developed for dry granular flows to an immersed environment. This will involve setting up and calibrating various sensors: high-speed cameras, force sensors, accelerometers and hydrophones.

In order to validate the device, measurements obtained during the impact of a single grain will first be carried out. An analysis will be carried out to compare our measurements with impact models for submerged particles. Secondly, measurements on granular avalanches will be carried out in order, on the one hand, to retrieve results published in the literature on flow dynamics and, above all, to characterise the elastic and hydro-acoustic emission during the avalanche.

The candidate will be responsible for completing the development of the tools required for the study. He/she will carry out the necessary numerical simulations and analyse the results. The results obtained will be presented at conferences. The results must be published in high-impact scientific journals.

Work Context

The Langevin Institute was created through the merger of two laboratories: the “Laboratory of Waves and Acoustics” and the “Laboratory of Physical Optics.” This brings together researchers from different backgrounds, all driven by the same passion: the study of all possible types of waves. The unit is organized to support cutting-edge scientific research and promote its development.

The Paris Institute of Earth Physics is a world-renowned geoscience research institute founded in 1921, associated with the CNRS, a component of Paris Cité University, and bringing together more than 500 people. The IPGP covers all disciplines of earth and planetary sciences through observation, experimentation, and modeling, at all scales of time and space.

Research topics are structured around four major themes: Earth and Planetary Interiors, Natural Hazards, Earth System, and Origins.

The IPGP is also responsible for certified services in volcanology, seismology, magnetism, gravimetry, and erosion. In particular, the IPGP's permanent observatories monitor the four active French volcanoes overseas in Guadeloupe, Martinique, Réunion, and Mayotte (REVOSIMA).

The IPGP houses powerful computing resources and state-of-the-art experimental and analytical facilities and benefits from first-rate technical support.

The IPGP's training and doctoral studies department offers its students training in geosciences that combines observation, quantitative analysis, and modeling, reflecting the quality, richness, and thematic diversity of the research conducted by the IPGP's teams.

The thesis will be carried out between the Langevin Institute and the IPGP seismology team. The IPGP seismology team, located on the same site as the Langevin Institute, works on seismic waves, which offer a unique window of observation on our planet. We are interested in understanding all the physical phenomena responsible for the generation, propagation, and measurement of these waves. Within our team, we cover all of these topics in detail in order to describe the physical processes involved in seismic sources (seismic faults, slow and transient deformations, volcanism, landslides, glaciers, ocean movements) and the properties of the environments they pass through (from the subsurface to the depths of the Earth). Our research activities include the development of new measurement instruments, the deployment of in situ sensors, data analysis, and modeling.