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Boundary layer development and shear stresses measurements around an oyster table ArchiMer
Kervella, Youen; Germain, Gregory; Gaurier, Benoit; Facq, Jean-valery; Cayocca, Florence; Lesueur, Patrick.
Oyster tables are artificial obstacles which are laid over muddy or sandy-muddy floors in intertidal areas. This study aims to show the current modifications related to the presence of the oyster table thanks to LDV measurement in a flume tank. Boundary layer development in different geometric configuration is underlined and suggests some important areas of velocity decrease and sediment transport modification. Shear stresses are also calculated near the bottom and around the table. The total shear stress in the water column exhibits an important increase when the flow passes through the oyster table, hence a flow energy decrease through dissipation. This study helps to understand the reasons for the increased sedimentation observed in some natural sites.
Tipo: Text
Ano: 2009 URL: http://archimer.ifremer.fr/doc/00022/13359/10388.pdf
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Caractérisation numérique et expérimentale des perturbations engendrées par la présence de tables ostréicoles ArchiMer
Kervella, Youen; Germain, Gregory; Gaurier, Benoit; Cayocca, Florence; Lesueur, Patrick.
Sur de nombreux sites ostréicoles, d’importants mouvements sédimentaires modifient les conditions d’exploitation. Les mouvements naturels sont modifiés par la présence des tables à huîtres, les phénomènes en jeu étant de deux ordres : la perturbation des courants de marée et la modification des conditions de houle. Nous présentons dans ce document la méthodologie mise en place pour améliorer la compréhension des perturbations physiques du milieu engendrées par l’implantation de tables ostréicoles et caractériser les modifications de l’écoulement. Les résultats obtenus, tant expérimentaux que numériques, sont présentés et les développements pour une extension du modèle à l’échelle d’un parc ostréicole sont discutés. Des essais expérimentaux réalisés à...
Tipo: Text Palavras-chave: Mesures LDV; Essais expérimentaux; Simulations numériques; Contraintes de cisaillement; Hydrodynamique côtière; Table ostréicole.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00011/12263/9044.pdf
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Development and validation of a sediment dynamics model within a coastal operational oceanographic system ArchiMer
Cayocca, Florence; Verney, Romaric; Petton, Sebastien; Caillaud, Matthieu; Dussauze, Morgan; Dumas, Franck; Le Roux, Jean-francois; Pineau-guillou, Lucia; Le Hir, Pierre.
The rising interest in environmental and ecosystem dynamics have lead coastal oceanographers to not only investigate the “traditional” physical parameters describing the ocean state and its dynamics (e.g. temperature, salinity, currents, water levels in coastal areas), but to also account for the dynamics of parameters describing its biogeochemical components. To that end, MARS3D regional and coastal modelling system has been coupled to ecosystem modules (ECO-MARS3D, ECO3M) as well as sediment dynamics modules (MARS3D-SEDIM): sediment, nutrient and primary production contents can be considered as the lower level environment and ecosystem descriptors of the “biogeochemical” ocean. Early investments into physical and biological analysis at the regional scale...
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00194/30572/29015.pdf
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Dynamics of sand and mud mixtures: a multiprocess-based modelling strategy ArchiMer
Le Hir, Pierre; Cayocca, Florence; Waeles, Benoit.
Mixed sediments are constituted of cohesive and non-cohesive materials with distinct behaviours that numerical models traditionally manage separately. This paper first introduces a rapid state of the Art in sediment transport modelling in order to point out the specific requirements for process-based models applied to mixed sediments. Based on a preliminary study by Waeles et al. (2007), which showed the validity of the advection approach to compute fine sand transport, a complete modelling strategy is described: it is applied to the suspended transport of sand and mud mixtures, and accounts for consolidation of mixed sediments. Special care is paid to the realistic representation of the structure and density of sand and mud mixtures, and to the...
Tipo: Text Palavras-chave: Sediment transport modelling; Mixed sediment; Sand; Mud; Suspension; Consolidation.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00028/13952/12567.pdf
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Evaluation of the risk of marine slope instability: A pseudo-3D approach for application to large areas ArchiMer
Sultan, Nabil; Cochonat, Pierre; Bourillet, Jean-francois; Cayocca, Florence.
This article presents a methodology developed to evaluate the instability of submarine slopes that extend over a large area. Special attention was paid to (1) the complex geometry (bathymetry) and the expanse of the slope, (2) the heterogeneity of the sediment, and (3) the distribution of the pore pressure. The safety factor was considered as a spatially varying quantity. The General Formulation (GLE, Fredlund and Krahn 1977), which fully satisfies equilibrium conditions, was used for evaluating the stability of the marine slope. The submarine slope failure, which occurred on 16 October 1979 during the construction of the new Nice airport, was studied in order to test the developed model. Geotechnical parameters were taken from experimental tests carried...
Tipo: Text Palavras-chave: Shear strength; Slope stability; Safety factor; Marine sediment; Finite element; Finite difference; Failure.
Ano: 2001 URL: http://archimer.ifremer.fr/doc/2001/publication-698.pdf
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Experimental and numerical characterization of an oyster farm impact on the flow ArchiMer
Gaurier, Benoit; Germain, Gregory; Kervella, Youen; Davourie, Julia; Cayocca, Florence; Lesueur, Patrick.
Shellfish farming, particularly oyster farms, suffers from strong siltation phenomena which are harmful to the production of shellfish. The lack of knowledge about the impact of an oyster farm on the wave propagation and on the flow remains a significant difficulty for the comprehension of sediment transport processes in coastal zones. These effects are one of the possible sources of sedimentation. The study presented here focuses on describing finely hydrodynamical phenomena (velocity fields, turbulence parameters) around oyster tables. The analysis is based on experimental trials carried out in a flume tank on reduced models of oyster tables. Experiments highlight the flow perturbations in the near field and constitute a database for validation of...
Tipo: Text Palavras-chave: Sediment dynamics; Oyster table; LDV measurement; Computational fluid dynamics; Porosity; Boundary layer.
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00043/15421/12974.pdf
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Experimental study of the near-field impact of an oyster table on the flow ArchiMer
Kervella, Youen; Germain, Gregory; Gaurier, Benoit; Facq, Jean-valery; Cayocca, Florence; Lesueur, Patrick.
Oyster farming structures are artificial obstacles which disturb tidal flow and wave propagation. These effects can induce modifications of erosion and sedimentation patterns, turbidity changes, local silting up and can be threatening for the shellfish farming itself. The understanding of the impact of these structures in terms of hydrodynamics and sediment dynamics in the far-field, i.e. at the scale of a bay, is a very challenging task. In order to investigate the far-field impact, it is very important to understand in the first place all the changes which occur at a smaller scale, i.e. at the scale of a single table for a farm consisting of oyster tables made of metallic wire structures on which porous bags of oysters are laid. This work is carried out...
Tipo: Text Palavras-chave: Sediment dynamics; Roughness length; Boundary layer; Particle Image Velocimetry; Laser Doppler Velocimetry; Flume; Oyster table.
Ano: 2010 URL: http://archimer.ifremer.fr/doc/2010/publication-7389.pdf
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Fine sediment dynamics in the Río de la Plata ArchiMer
Fossati, Monica; Cayocca, Florence; Piedra-cueva, Ismael.
This paper investigates the main characteristics of the fine sediments dynamics in a very complex and extensive inner shelf area located in South America, the Río de la Plata. The results derive from a 5 yr international research program that allowed intensive data acquisition throughout the area, as well as the development of the first numerical model investigating sediment dynamics at a regional scale in the area. The model is based on the MARS3D suite: it computes the regional tide- and wind-induced circulation, as well as sediment mixtures dynamics (erosion, advection and deposition of several sedimentary variables). Erosion due to wave action is taken into account thanks to the use of SWAN. The hydrodynamic and wave models were calibrated against...
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00195/30577/29017.pdf
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Impact des facteurs environnementaux et des pratiques conchylicoles sur la baie du Mont Saint-Michel et la production conchylicole. Etude de scenarii par modélisation. Programme Liteau 3. Rapport Final ArchiMer
Cugier, Philippe; Frangoudes, Katia; Blanchard, Michel; Mongruel, Remi; Perez, Jose; Le Mao, Patrick; Robin, T.; Fontenelle, Guy; Mazurie, Joseph; Cayocca, Florence; Pouvreau, Stephane; Olivier, F..
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00026/13707/10862.pdf
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Impact hydrodynamique de la mise en place d’un parc d’hydroliennes en Baie du Mont Saint-Michel ArchiMer
Batifoulier, Francois; Kervella, Youen; Laborde, Renaud; Cuny, Jérôme; Caillaud, Matthieu; Lazure, Pascal; Cayocca, Florence.
Les fortes vitesses rencontrées à l’entrée de la Baie du Mont Saint-Michel font de cet environnement macro-tidal un endroit privilégié, en termes de ressources énergétiques, pour l’implantation d’une ferme d’hydroliennes. Afin d’établir plus précisément son potentiel énergétique et d’évaluer l’impact de l’implantation de telles machines sur son hydrodynamisme, une modélisation hydrodynamique de la Baie du Mont Saint-Michel est mise en oeuvre à l’aide du modèle de circulation régionale MARS3D (LAZURE & DUMAS, 2008) dans sa version tridimensionnelle. La validation hydrodynamique de cette configuration est réalisée à partir de comparaisons à des mesures courantologiques récentes (KERVELLA, 2010). A partir de cette modélisation, une cartographie du...
Tipo: Text Palavras-chave: Modélisation régionale; Hydroliennes; Baie du Mont Saint-Michel; Hydrodynamisme; Potentiel énergétique.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00195/30599/29055.pdf
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Influence of bottom trawling on sediment resuspension in the 'Grande-Vasière' area (Bay of Biscay, France) ArchiMer
Mengual, Baptiste; Cayocca, Florence; Le Hir, Pierre; Draye, Robin; Laffargue, Pascal; Vincent, Benoit; Garlan, Thierry.
Sea trials were performed on two zones with different fishing efforts on the continental shelf of the Bay of Biscay ('Grande-VasiSre' area of muddy sand) in order to assess particulate matter resuspension and seabed disturbances (i.e., penetration, reworking, grain size changes) induced by different types of trawls. Optical and acoustic measurements made in the water column indicate a significant trawling-induced resuspension mainly due to the scraping action of doors. It manifests as a highly dynamic turbid plume confined near the seabed, where suspended sediment concentrations can reach 200 mg l(-1). Concentration levels measured behind an "alternative" configuration (trawls with jumper doors instead of classical doors penetrating the sediment) are...
Tipo: Text Palavras-chave: Bottom trawling; Sedimentresuspension; Seabed disturbance; Erosion flux; Bay of Biscay.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00353/46428/51396.pdf
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Modélisation hydro-sédimentaire de la baie du Mont Saint-Michel ArchiMer
Cayocca, Florence; Dussauze, Morgan; Le Hir, Pierre; Bassoullet, Philippe; Jestin, Herve.
A numerical model for hydrodynamics and sediment transport is applied to Mont Saint Michel Bay, where ecological concerns are related to sediment transfers. Recent current datasets recorded on the tidal flat show the wind influence on the currents during neap tide. They are compared to model outputs. The simulation of sediment transfers driven by tides and waves accurately mimics the sediment repartition in the Bay.
Tipo: Text Palavras-chave: Turbidité; Sédiments cohésifs; Modèle; Courant; Mont Saint Michel.
Ano: 2006 URL: http://archimer.ifremer.fr/doc/2006/acte-6274.pdf
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Modélisation morphodynamique d'une embouchure tidale : Application aux Passes d'entrée du Bassin d'Arcachon ArchiMer
Cayocca, Florence.
The Arcachon tidal inlet exhibits a particularly active morphology due to strong tidal currents and rough wave conditions. During the past 300 years, maximum and minimum extents of the Cap Ferret sand spit have resulted in a difference of 8 km while two channels have alternatively allowed circulation between the lagoon and the ocean. A bidimensional horizontal morphodynarnic model was developed in order to simulate the system evolution under tidal forcing alone or under combined tide and wave action. Modelling at a scale of decades requires the definition of mean annual wave and tide conditions which are representative with respect to sediment transport. Medium term results thus give general trends of evolution. Driven by these average conditions and...
Tipo: Text Palavras-chave: Littoral drift; Sediment transport; Tide; Waves; Arcachon lagoon; Tidal inlet; Modelling; Morphodynamic; Dérive littorale; Transport sédimentaire; Marée; Houle; Bassin d'Arcachon; Modèle; Morphodynamique.
Ano: 1996 URL: http://archimer.ifremer.fr/doc/1996/these-4520.pdf
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Modelling Fine Sediment Dynamics: Towards a Common Erosion Law for Fine Sand, Mud and Mixtures ArchiMer
Mengual, Baptiste; Le Hir, Pierre; Cayocca, Florence; Garlan, Thierry.
This study describes the building of a common erosion law for fine sand and mud, mixed or not, in the case of a typical continental shelf environment, the Bay of Biscay shelf, characterized by slightly energetic conditions and a seabed mainly composed of fine sand and muddy sediments. A 3D realistic hydro-sedimentary model was used to assess the influence of the erosion law setting on sediment dynamics (turbidity, seabed evolution). A pure sand erosion law was applied when the mud fraction in the surficial sediment was lower than a first critical value, and a pure mud erosion law above a second critical value. Both sand and mud erosion laws are formulated similarly, with different parameters (erodibility parameter, critical shear stress and power of the...
Tipo: Text Palavras-chave: Sand-mud mixture erosion; Numerical modelling; Non-cohesive to cohesive transition.
Ano: 2017 URL: http://archimer.ifremer.fr/doc/00394/50588/51280.pdf
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Preface of the CSR Supplement Issue: Proceedings of the 9th International Conference on Nearshore and Estuarine Cohesive Sediment Transport Processes ArchiMer
Le Hir, Pierre; Toorman, Erik; Cayocca, Florence; Verney, Romaric.
Tipo: Text
Ano: 2011 URL: http://archimer.ifremer.fr/doc/00041/15250/12620.pdf
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Remaniements sédimentaires superficiels sur l'estran occidental de la baie du Mont Saint-Michel ArchiMer
Bonnot-courtois, C; Bassoullet, Philippe; Tessier, B; Cayocca, Florence; Le Hir, Pierre; Baltzer, A.
In order to define and quantify the rhythm and amplitude of the processes of erosion and sedimentation on broad tidal flats, in situ measurements of sediment elevation have been performed in the western part of the Mont-Saint-Michel bay. The amplitude of reworking is generally low (< ± 5 cm), and variable from west to east. The wind influence on tidal currents and surficial reworking emphasizes erosion phases rapidly followed by accretion of similar amplitude on the whole tidal flat. A numerical model for hydrodynamics and sediment transport is applied to Mont Saint Michel Bay, where ecological concerns are related to sediment transfers.
Tipo: Text Palavras-chave: Sediment transport; Numerical model; Erosion sedimentation budget; "In situ" measurements; Tidal sandy mud flat; Transport sédimentaire; Modèle numérique; Bilan érosion sédimentation; Mesures in situ; Estran sablo vaseux.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6279.pdf
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Sedimentary processes in a shellfish farming environment, Mont Saint Michel Bay, France ArchiMer
Cayocca, Florence; Bassoullet, Philippe; Le Hir, Pierre; Jestin, Herve; Cann, Philippe.
Mont Saint Michel Bay is a 30 km wide bay located on the French side of the English Channel. The tidal range reaches 14 m during spring tides, which leads, along with the gentle slope of the bathymetry, to a tidal flat up to 11 km wide. The sedimentary coverage exhibits strong longshore and cross-shore gradients, with purely muddy environments to the west of the domain, and pure sands to the east, where the natural channels of three incoming rivers induce rapid morphological changes. The contributions of tides and waves to sedimentary processes are analysed by means of numerical modelling and results of field observations. Maximum tidal bottom shear stresses are shown to account for the sediment distribution throughout the bay, while the longshore gradient...
Tipo: Text
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6278.pdf
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