Parallelization of a relaxation scheme modelling the bedload transport of sediments in shallow water flow

In this work we are interested in numerical simulations for bedload erosion processes. We present a relaxation solver that we apply to moving dunes test cases in one and two dimensions. In particular we retrieve the so-called anti-dune process that is well described in the experiments. In order to be able to run 2D test cases with reasonable CPU time, we also describe and apply a parallelization procedure by using domain decomposition based on the classical MPI library.Comment: 19 page

HOODESolver.jl: A Julia package for highly oscillatory problems

International audienc

Aéroacoustique numérique d'un écoulement tourbillonnaire

Nous avons développé une méthode particules-maillage pour un écoulement plan compressible. La méthode est dérivée de la méthode Particle-in-Cell pour les écoulements incompressibles. Dans la deuxième partie nous utilisons la méthode des rayons modifiée pour le calcul de propagation du bruit dans un parc éolien. A travers les résultats numériques, nous discutons de la validité de la méthode. Nous montrons notamment plusieurs limitations de cette approche mais aussi des solutions permettant de l'améliorer.A discrete vortex method for unsteady, compressible, two-dimensional and inviscid flow is developped. The method is based on the incompressible vortex-in-cell method. The second part concerns the use of a modified ray theory called "gaussian beam approch" to compute the noise emission in a wind park. The results of the numerical experiments and the validity of the method are discussed. The present limitations of the method are shown and several ways of improving them are indicated.LE HAVRE-BU Centrale (763512101) / SudocSudocFranceF

An asymptotic preserving scheme for

A new scheme for discretizing the P1 model on unstructured polygonal meshes is proposed. This scheme is designed such that its limit in the diffusion regime is the MPFA-O scheme which is proved to be a consistent variant of the Breil-Maire diffusion scheme. Numerical tests compare this scheme with a derived GLACE scheme for the P1 system

Guiding center simulations on curvilinear grids*

Semi-Lagrangian guiding center simulations are performed on sinusoidal perturbations of cartesian grids, and on deformed polar grid with different boundary conditions. Key ingredients are: the use of a B-spline finite element solver for the Poisson equation and the classical backward semi-Lagrangian method (BSL) for the advection. We are able to reproduce standard Kelvin-Helmholtz and diocotron instability tests on such grids. When the perturbation leads to a strong distorted mesh, we observe that the solution differs if one takes standard numerical parameters that are used in the cartesian reference case. We can recover good results together with correct mass conservation, by diminishing the time step

Extension of ALE methodology to unstructured conical meshes

Titre du volume 32 : CEMRACS'10 research achievements: Numerical modeling of fusion. Marseille, France, 19 Juillet - 27 Août 2010 E. Cancès, N. Crouseilles, H. Guillard, B. Nkonga and E. Sonnendrücker (Eds.)International audienceWe propose a bi-dimensional nite volume extension of a continuous ALE method on unstructured cells whose edges are parameterized by rational quadratic Bezier curves. For each edge, the control point possess a weight that permits to represent any conic (see for example [LIGACH]) and thanks to [WAGUSEDE,WAGU], we are able to compute the exact area of our cells. We then give an extension of scheme for remapping step based on volume uxing [MARSHA] and selfintersection ux [ALE2DHAL]. For the rezoning phase, we propose a three step process based on moving nodes, followed by control point and weight re-adjustment. Finally, for the hydrodynamic step, we present the GLACE scheme [GLACE] extension (at rst-order) on conic cell using the same formalism. We only propose some preliminary rst-order simulations for each steps: Remap, Pure Lagrangian and nally ALE (rezoning and remapping)

Spatial and Temporal Variation in a Caribbean Herbivorous Fish Assemblage

The present work analyses the spatial and temporal variations of the herbivorous fish assemblage on 10 coral reef sites in the Caribbean island of Guadeloupe (French West Indies). The herbivorous fish assemblage was assessed by visual census along band transects; environmental data were collected to determine the relationship between environmental conditions and temporal and spatial variations in herbivorous fish abundance and distribution. Spatial variation in species abundance was related to variation of the benthic cover (e.g., coral and algae), depth, and protection status among sites. Short-term fluctuations of herbivorous fishes on the reef flats were linked to tide, swell, and wind, whereas longterm variations were seasonal and highly correlated to annual water temperature oscillations