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Research

27/04/2012

Studying natural hazards to understand and prevent risks

Jacques Sainte-Marie

We met with Jacques Sainte-Marie, researcher in the Bang project team at the Inria 
Paris–Rocquencourt research centre.

Can you tell us about the subject of your research?

Our research work concerns natural hazards (tsunamis, swells, erosion, floods, etc.) and industrial risks (dam failures, pollution) associated with physical phenomena that are both complex and hard to describe.

We are therefore interested in stratified flows (where flow is not vertically uniform), for example variable density flows (thermohaline stratification for oceans). Stratification can also be related to the presence of pollutants, biological species and sediments in the water. We also study the interactions arising when fluid comes into contact with structures (swell in a harbour).

We endeavour to develop good models for these complex flows; these models must be adapted to the physical phenomena studied, effectively simulated and approved. The models derived from fluid mechanics, typically the Navier-Stokes equations, enable a description of the hydrodynamics (wave and current propagation).

The team's research programme is focused on modeling, mathematical and computational analysis, and the simulation of models that are less complex than the Navier-Stokes equations, but break away from the traditional hypotheses that one finds in so-called "shallow" flow models. However, the analysis and simulation of these models are delicate operations and strong points in the team's research work.

What societal challenges does this research help meet?   

Map of seabed off the coast of Japan with the epicentre of the March 2011 earthquake (red circle) - © Bang - Inria

Our objective is to provide simulating and forecasting tools for the above-mentioned phenomena. These tools can be used to size structures (dams, dykes) to handle sea flooding or other scenarios.

We are currently working on problems related to the interaction of hydrodynamics and biology. Water contains biological species that are transported by the fluid, but also live, grow and carry out photosynthesis within the fluid. In addition to hydrodynamics, the issue is therefore to offer an accurate representation of the biological quantities which often have varying time constants that differ from those of hydrodynamics. The benefits of this research are widespread, such as for forecasting ocean carbon capture or producing biofuels based on micro-algae cultivated in ponds. This research work is carried out in collaboration with the Biocore IPT. Furthermore, the project we have jointly proposed for the exploitation of micro-algae, entitled GREENSTARS, is one of the winners of the "Institute of Excellence on Carbon-Free Energies" call for projects.

Are there currently any concrete applications? If so, what partners are you collaborating with?

The computational simulation models and tools that we are developing are regularly transferred to researchers in geoscience, hydraulics and other fields, as well as industrial partners such as EDF R&D and the SME Naskeo.

As such, an extended Saint-Venant model that we developed has been implemented in the EDF simulation codes and is being used to prevent risks associated with flood waves.

Our team is working in partnership with the French Ministry for Ecology and Sustainable Development (for which I work). At the application level, we have 3 types of partners:

  • partners in the academic world, such as the IPGP (Institut de Physique du Globe de Paris - Paris Institute of Earth Physics), INRA, oceanographic laboratories, etc.
  • industrial partners, such as EDF and Naskeo (www.naskeo.com)
  • public services in charge of coastal and port developments and the management of natural risks, including flooding

Keywords: Navier-Stokes equation Simulation Modélisation Mécanique des fluides

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