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Terre Univers Environnement

Propagation of viscoplastic surges over complex topographies

stage de 5-6 mois (1er semestre 2018)

par Stages - 29 novembre 2017

Laboratoire(s) de rattachement : IRSTEA Grenoble (Unité de Recherche Erosion Torrentielle, Neige et Avalanches) / ENS Lyon (Unité de Mathématiques Pures et Appliquées)
Encadrants et co-encadrants : Guillaume Chambon (IRSTEA Grenoble) / Paul Vigneaux (ENS Lyon)
Lieu Grenoble (+déplacements fréquents à Lyon)
Niveau de formation & prérequis : M2 Géophysique, Physique, ou Mécanique des fluides
Mots clés : complex fluid, depth-averaged model, rheology, free-surface flow, natural hazard

Viscoplastic, or yield-stress, fluids are involved in numerous geophysical and industrial applications. These materials have the property to behave either as fluids or solids depending on the applied loading. Due to the coexistence in the flows of fluid and solid zones whose respective boundaries are a priori unknown, simulating the propagation and deposition of free-surface viscoplastic surges remains challenging, in particular when the basal topography is complex. In addition, most existing models for free-surface flows rely on depth-averaged approaches, for which efficient numerical solvers can be implemented, but which require a good knowledge of the internal dynamics of the surges.

The objective of this project is to compare the predictions of a recently-developed, depth-averaged numerical model to well-controlled laboratory experiments. The model relies on an optimized numerical scheme able to capture very precisely the final deposit of the surge. However, several assumptions used in the modeling need to be tested. The experiments will be performed in a dam-break configuration, with a complex basal topography and a model viscoplastic fluid with known rheological properties (polymeric microgel). An originality of the project will be the use of synthetic topographies generated by 3D printing, in order to have a precise match with the simulations. The propagation of the fluid and the final deposit will be monitored through optical stereoscopy techniques, and compared to the numerical predictions. We will focus, in particular, on the influence of basal roughness, in relation with the slip condition taken into account in the model.

To apply, send CV + motivation letter to guillaume.chambon@irstea.fr and Paul.Vigneaux@math.cnrs.fr

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