Missions

Some turbulent flow configurations have been observed to be prone to random bifurcations, i.e. the flow regime switches from one type of behavior to another over a random period of time without any external modification.

To predict numerically turbulent flows, LES (Large-Eddy Simulation) allows to reduce computational cost by explicitly solving only the largest spatiotemporal scales of the flow. In this context, subgrid scale (SGS) closures are key ingredients to account for the impact of unresolved fine scale variables over resolved larger scales variables. In practice, these models are usually deterministically asserved to large scale resolved quantities and obtained through the combination of theoretical and empirical considerations. The ability of LES to predict bifurcations needs then to be assessed, and the influence of the SGS closures need to be better understood. This is the first objective of this work.

This project is included in a more ambitious project dedicated to the development of a strategy for identifying the precursor signals of rare events and/or bifurcations in turbulent flows. The first step is therefore to build up a database of these kind of events (both numerically and experimentally).

Activities

To numerically predict turbulent flows, the MOST team at LEGI contributes on the development of YALES2 (http://www.coria-cfd.fr/index.php/YALES2), a simulation tool for incompressible flows which aims to model turbulent flows with large meshes size on massively parallel supercomputers.

The activities would include the revisiting of SGS modeling to improve prediction of bifurcations, and the development of a dynamic control to favor bifurcations in simulations.

Skills

The candidate must hold a doctorate degree in fluid mechanics or applied mathematics.
- Computational Fluid Dynamics, Physics and modeling of Turbulence, Numerical analysis, Object-Oriented Programming
- Writing skills in English, ability to formulate/work on a scientific project
- Ability to work in a team

Work Context

Joint Research Unit (UMR 5519) of the Centre National de la Recherche Scientifique (CNRS), and the University Grenoble-Alpes (UGA), LEGI carries out a wide range of research activities with a common ground: fluid mechanics and related transport phenomena.

The recruited person will be assigned to the MOST team. The research activities of the MOST (Modelling and Simulation of Turbulence) team focus on the numerical prediction of turbulent and multiphase flows with a broad range of objectives from fundamental understanding of flow properties to technologies optimization. The research team has the ambition to address all the needed scientific fields to understand turbulent and multiphase flows from simulation: numerical methods, turbulence models, physics of fluids, flow control...

The main objective is to develop numerical tools to efficiently predict and to deeply understand flows in more and more physically and geometrically complex configurations. This activity is inherently multidisciplinary with strong collaborations with other scientific fields, as applied mathematics or statistical physics. Fluid mechanics is ubiquitous in geophysical and industrial applications. Better understanding of flows will help to address major challenges to deal with new energy and environmental constraints. Collaborations with experts in geosciences and in renewable energy development have been set-up to respond to these societal issues.

Constraints and risks

No risk identified

Additional Information

Keywords: turbulence, bifurcations, Large-Eddy Simulation, subgrid-scale modeling, incompressible flow