Description du sujet de thèse

Floods caused by breaches of river dikes are among the major natural hazards, whose intensity and frequency increase with climate drift. Still unexplained observations have been reported when these breaches are located above a paleochannel made up of decompacted and highly erodible sediments: i) the formation of a large erosion pit during a breach, iii) a flood wave much more powerful than water in terms of transport capacity and destruction of buildings. Analysis of the state of practices does not show a model capable of explaining these observations, as well as the orders of magnitude of documented historical events.

Predicting erosion pits and deposit morphology is a major challenge in the context of flood risk. These phenomena are based on the description of a complex flow formed by particles suspended in water, whose solid concentration is controlled both by soil erosion and by particle sedimentation processes. The objective of the thesis is to have a theoretical and numerical model of a free-surface flow on an erodible bed, satisfactorily explaining two documented historical cases of flooding by river dike failure. The expected outcome is to allow a physically based assessment of the dimension of the energy dissipation zones near dike breaches.

Skills:

- solid knowledge of fluid mechanics and multiphase flows

- solid knowledge of numerical methods

- knowledge of free-surface flows, granular flows

- proven experience in numerical simulation (finite elements, finite volumes, CFD, LES, etc.)

- proficiency in basic scientific computing tools (Fortran, C/C++, Python, Linux)

- fluency in English and proven international experience

Contexte de travail

This work is part of the PEPR Math-Vives Targeted Project Complexflows, which aims to promote and structure the interactions of mathematics with other sciences around current issues. The thesis will be co-directed by F. Radjaï (LMGC, ED I2S 166) and S. Bonelli (RECOVER, ED SPI 353). It will be co-supervised by L. Girolami (RECOVER), C. LUCAS (Institut Denis Poisson), O. Delestre (Laboratoire J.A. Dieudonné), Andrea Bondesan (DMFI, Parma, Italy), and A. Wautier (RECOVER). It will be located at the UMR RECOVER in Aix-en-Provence.

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