Thesis: Experimental turbulence for rotating stratified geophysical flows. (M/F)

Description of the thesis topic

Experimental turbulence for rotating stratified geophysical flows.

Geophysical flows generally result from the interaction of various forces, such as planetary rotation, buoyancy forces, turbulence and topography. This is the case in the Earth’s atmosphere or oceans (thin layers), but also in deeper fluid layers (thick layers) such as the Earth’s liquid outer core. These generic ingredients could be essential to explain certain geodetic observations (e.g., variations in the Earth’s axis of rotation), or the generation of the magnetic field of the primitive Earth or Moon. However, many of the characteristics of these geophysical flows remain poorly constrained to this day. For example, the most advanced numerical models (e.g. atmospheric and oceanic GCMs, or for geodynamo) cannot resolve the small and medium (i.e. intermediate) scales of these flows. What’s more, the dynamics of near-boundary flows and the associated stress are largely unknown, even though they are essential for coupling geophysical flows to topography.

As it is difficult to model such turbulent flows using simulations, laboratory experiments will be used. For this purpose, the candidate will have access to an experimental room equipped with several experimental devices (see details below). We will gradually increase the complexity of the experiments, starting with the study of :
– Pattern formation on a dynamic topography with rotation and oscillating flows.
– Effects of buoyancy on rotating fluid dynamics (e.g. Rayleigh-Taylor instability).
– Fluid-solid stress due to rotating (stratified) turbulence above the topography.

Particular attention will be paid to linking experimental observations to theoretical predictions, especially in linear and (if possible) weakly non-linear regimes. A long-term objective is to validate the parametric models currently being studied by the community.

Work Context

The Centre National de la Recherche Scientifique is one of the world’s leading research institutions. To meet the major challenges of today and tomorrow, its scientists explore life, matter, the Universe and the workings of human society.
Internationally recognized for the excellence of its scientific work, the CNRS is a benchmark in the world of research and development, as well as for the general public.

The thesis will be effectuated within the ISTerre laboratory.
ISTerre is a Joint Research Unit of Grenoble Alpes University, CNRS, USMB, IRD and Gustave Eiffel University, located 1381 rue de la Piscine 38400 Saint-Martin d’Hères and on the Bourget du Lac Science Campus.
It is part of the Observatoire des Sciences de l’Univers de Grenoble (OSUG) and the PAGE research cluster of the Université Grenoble Alpes (UGA).
It employs around 300 people and has an average annual budget of €7 million.
It is organized around 9 research and service teams, with the scientific objective of studying the physics and chemistry of planet Earth, with a particular focus on coupling observations of natural objects with experimentation and modeling of the associated complex processes.
ISTerre also carries out solid Earth observation missions, and hosts and maintains national fleets of geophysical instruments, as well as a data center.

The thesis will be carried out in the Geodynamo team.
The Geodynamo team focuses on the study of the Earth’s magnetic field and the physics of the Earth’s core. We use :
– Analog experiments (such as DTS or ZoRo).
– Innovative inversion techniques to determine core flow from magnetic field measurements.
– Direct numerical simulations and theoretical models.

The doctoral school will be ED STEP.