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A 3D study of the bubble sweep-down phenomenon around a 1/30 scale ship model ArchiMer
Mallat, Bachar; Germain, Gregory; Billard, Jean-yves; Gaurier, Benoit.
The bubble sweep-down phenomenon around oceanographic research vessels generates acoustic disturbances. A specific experimental protocol in a wave and current circulating tank is used to study this phenomenon around a 1/30 scale ship model in a configuration with current, waves and ship motions. 3D visualizations of the bubble clouds and Stereo-PIV (Particle Image Velocimetry) measurements results, both obtained in the bow vicinity of the ship model, are presented in this paper. The behaviour of the breaking wave with bubble generation is studied and the spatial evolution of the bubble clouds is investigated. It is demonstrated that the bubble cloud generation is mainly conditioned by the ascending vertical velocity of the flow near the bow. It is observed...
Tipo: Text Palavras-chave: Bubble sweep-down; Breaking wave; Bow wave; Fluid-structure interaction; Flume tank.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00453/56423/58534.pdf
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A Synthetic turbulence model for numerical simulation of marine current turbine ArchiMer
Carlier, Clement; Pinon, Gregory; Gaurier, Benoit; Germain, Gregory; Rivoalen, Elie.
The ambient turbulence intensity is a key factor in the study of marine current turbines. Indeed recent studies have shown that ambient turbulence intensity highly modifies the behavior of horizontal axis marine current turbines. Consequently numerical simulations have to represent the ambient turbulence or at least its effects on the performance and wake of the turbines. This paper presents the latest numerical developments carried out at LOMC in collaboration with IFREMER in order to take into account the effects of ambient turbulence.
Tipo: Text
Ano: 2015 URL: http://archimer.ifremer.fr/doc/00252/36293/34822.pdf
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Account of ambient turbulence for turbine wakes using a Synthetic-Eddy-Method ArchiMer
Pinon, Gregory; Carlier, Clement; Fur, Arnaud; Gaurier, Benoit; Germain, Gregory; Riyoalen, Elie.
The present paper aims at describing the use of a Synthetic-Eddy-Method (SEM), initially proposed by Jarrin et al. [12], in the 3D Lagrangian Vortex method framework. The SEM method is used here in order to generate a far-field incoming flow with a prescribed ambient turbulence intensity. However, for the account of the diffusive term in the Navier-Stokes equations, a classical Particle Strength Exchange model with a LES eddy viscosity is used. Firstly, the general characteristics of the Synthetic-Eddy-Method will be presented together with its integration in the framework of the developed 3D unsteady Lagrangian Vortex software [27]. The capability of the ambient turbulence model to reproduce a perturbed flow that verifies any turbulence intensity I∞ and...
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Ano: 2017 URL: http://archimer.ifremer.fr/doc/00389/50002/50587.pdf
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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 d'effets de sillages rencontrés en milieu offshore ArchiMer
Gaurier, Benoit; Germain, Gregory; Le Boulluec, Marc; Giry, Eric; Fontaine, E..
The interactions between several cylinders placed in close proximity are the subject of many studies, because of the strong repeated loads that they create on these structures. For flexible or mobile structures, the wake effects can produce large amplitudes motions. These displacements can be higher than those considered during the lock-in of a single cylinder, to reach several diameters. Depending the initial spacing, they lead sometimes to clashes with potentially high intensity, between the cylinders. To better understand these phenomena, an experimental study was carried out, bearing on the interaction between two models of tensioning buoy supporting hybrid risers. After checking that the models used were able to correctly reproduce the movements...
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Ano: 2007 URL: http://archimer.ifremer.fr/doc/00023/13439/10447.pdf
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Caractérisation expérimentale du sillage généré par une hydrolienne - Influence du taux de turbulence ambiant ArchiMer
Maganga, Fabrice; Germain, Gregory; Facq, Jean-valery; Gaurier, Benoit; Rivoalen, Elie; Pinon, Grégory.
Le fonctionnement d’une hydrolienne est régi par les caractéristiques de l’écoulement incident. Cet article présente les résultats d’une étude expérimentale visant à déterminer les effets du taux de turbulence de l’écoulement ambiant sur le fonctionnement d’une hydrolienne et le sillage généré. Les essais expérimentaux ont été réalisés dans la veine hydrodynamique à surface libre de l’Ifremer, dont on peut faire varier le taux de turbulence de l’écoulement de 5 à 25%. Le prototype utilisé est une turbine tri-pales à axe horizontal de 0,7 m de diamètre (échelle 1/30). Des cartes de vitesses moyennes, de taux de turbulence, mais également d’énergie cinétique turbulente et de contrainte de cisaillement ont été obtenus à partir de mesures par vélocimétrie...
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Ano: 2010 URL: http://archimer.ifremer.fr/doc/00022/13355/10386.pdf
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Caractérisation expérimentale et numérique d’hydroliennes : études de deux hydroliennes en interaction ArchiMer
Carlier, Clement; Pinon, Gregory; Mycek, Paul; Gaurier, Benoit; Germain, Gregory; Rivoalen, Elie.
The development of marine current turbines arrays still needs nowadays many studies among which we can find the study of interactions between devices. In order to highlight these interactions effects, experiments were carried out in the IFREMER’s (Boulogne-sur-Mer) flume tank. Those experiments used 3-bladed horizontal axis marine current turbines prototypes, regulated in rotation speed. To complete these experiments, a three-dimensional numerical tool is developed at the LOMC (Université du Havre) to simulate one or more turbines in a free upstream current. We present hereafter the numerical and experimental results obtained in the scope of the study of elementary interaction between two turbines axially aligned with the upstream current.
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00247/35806/34320.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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Couche limite et sillage rencontrés sur un chalut de fond ArchiMer
Bouhoubeiny, Elkhadim; Germain, Gregory; Druault, Philippe; Gaurier, Benoit; Facq, Jean-valery; Bacchetti, Thomas.
Flow field measurements around a bottom trawl are conducted using Time Resolved PIV method. Using the Proper Orthogonal Decomposition (POD) for such investigation, it is demonstrated the effectiveness of this procedure to characterize the boundary layer above the horizontal part of this porous structure and to extract the large scale spatial flow structure and their associated frequencies in the wake of the cod-end.
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Ano: 2011 URL: http://archimer.ifremer.fr/doc/00037/14815/12127.pdf
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Développements numériques pour la modélisation du comportement et du sillage d'hydroliennes ArchiMer
Mycek, Paul; Pinon, Gregory; Germain, Gregory; Rivoalen, Elie; Gaurier, Benoit.
Developments of new marine current turbines farm are subject to a better understanding of interactions effects between the turbines. Experimental trials have been realised in the wave and current flume of IFREMER Boulogne-sur-Mer, on a three bladed horizontal axis marine current turbine in order to characterise the elementary interaction between two turbines aligned with the current. At the same time, a three-dimensional numerical software has been developed in order to model the flow behind a marine current turbine. The software is based on a Lagrangian Vortex Method. It enables to evaluate the forces and moments onto the rotor as well as the flow fields around the turbine. Most of the previous numerical studies regarding interaction between devices only...
Tipo: Text
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00141/25200/23360.pdf
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Effet des concrétions marines sur le comportement hydrodynamique de structures circulaires ArchiMer
Gaurier, Benoit; Germain, Gregory; Facq, Jean-valery; Baudet, L.; Birades, M.; Schoefs, F..
The presence of marine growth on underwater parts of jackets significantly increases diameter and roughness of tubular members of these structures. This paper escribes an experimental study carried out in the circulating tank of Boulogne-sur-mer which aim to quantify the hydrodynamical drag and added-mass coefficients of a circular cylinder encrusted with rigid and large-size biofouling, such as coral. Two different kinds of roughness are studied and compared to a reference cylinder. These coefficients are obtained from trials with current only, with imposed motions or with a combination of imposed motions and current. Results show that these coefficients are from 1.5 to 4 times higher 1 than those obtained for the reference cylinder. Nevertheless,...
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Ano: 2014 URL: http://archimer.ifremer.fr/doc/00247/35821/34349.pdf
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Etude expérimentale du phénomène d’entraînement de bulles à l’étrave des navires scientifiques ArchiMer
Delacroix, Sylvain; Germain, Gregory; Billard, Jean-yves; Gaurier, Benoit; Facq, Jean-valery; Bacchetti, Thomas.
The bubble sweep-down phenomenon around the hull of scientific vessels leads to a disruption of the acoustic waves emitted by the sonars, and a loss of productivity during the acoustic surveys. Numerical or experimental tools used to study this phenomenon still have limitations, mainly due to scale effects on bubbles generation. An innovative method in a circulating tank, using numerical simulations and a motions generator, has been developed. Two mechanisms of air entrainment have been described, as well as the influence of waves characteristics and turbulence on bubbles generation.
Tipo: Text
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00247/35807/34321.pdf
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Etude expérimentale et numérique du comportement d’hydroliennes à axe horizontal ArchiMer
Carlier, Clement; Mycek, Paul; Gaurier, Benoit; Germain, Gregory; Pinon, Gregory; Rivoalen, Elie.
Le développement de fermes d'hydroliennes a suscité et suscite toujours de nombreuses études parmi lesquelles figure l’étude des effets d'interactions entre les machines. Afin de comprendre ces effets d'interactions des essais expérimentaux ont été effectués dans un bassin à houle et courant sur des maquettes d’hydroliennes 3 pales à axe horizontal, régulées en vitesse de rotation. Ces essais portent sur la caractérisation du fonctionnement d’une, puis de deux hydroliennes alignées avec le courant à partir de mesure de performance et de sillage. En parallèle, un code numérique tridimensionnel est développé pour modéliser une ou plusieurs hydroliennes dans un écoulement. On présente ici les résultats numériques et expérimentaux, obtenus pour deux points de...
Tipo: Text Palavras-chave: Energies marine; Hydroliennes; Simulation numérique; Méthode vortex; Méthode lagrangienne; Essais expérimentaux.
Ano: 2014 URL: http://archimer.ifremer.fr/doc/00212/32341/30781.pdf
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Étude numérique du comportement d'hydroliennes à axe horizontal : vers une modélisation d'un parc d'hydroliennes ArchiMer
Mycek, Paul; Gaurier, Benoit; Germain, Gregory; Pinon, Gregory; Rivoalen, Elie.
L’implantation et le développement de fermes d’hydroliennes sont soumis à la compréhension des effets d’interaction entre machines. Des essais expérimentaux ont été réalisés dans le canal à houle et courant de l’IFREMER à Boulogne-sur-Mer, sur des maquettes d’hydrolienne 3 pales à axe horizontal, dans le but de caractériser les interactions entre deux hydroliennes alignées avec le courant. En parallèle un code numérique tridimensionnel est développé pour modéliser l'écoulement derrière une hydrolienne. Ce code de calcul est basé sur la méthode Vortex. Il permet entre autres de calculer les efforts et moments sur le rotor ainsi que de tracer des cartes de vitesses en aval de l'hydrolienne. La plupart des études numériques portant sur les interactions entre...
Tipo: Text Palavras-chave: Énergies marines; Simulation numérique; Méthode vortex; Méthode lagrangienne; Essais expérimentaux; Hydroliennes.
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00141/25197/23307.pdf
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Evaluation of the durability of composite tidal turbine blades ArchiMer
Davies, Peter; Germain, Gregory; Gaurier, Benoit; Boisseau, Amelie; Perreux, Dominique.
The long term reliability of tidal turbines is critical if these structures are to be cost-effective. Optimised design requires a combination of material durability models and structural analyses. Composites are a natural choice for turbine blades but there are few data available to predict material behaviour under coupled environmental and cycling loading. This paper addresses this problem, by introducing a multi-level framework for turbine blade qualification. At the material scale static and cyclic tests have been performed, both in air and in seawater. The influence of ageing in seawater on fatigue performance is then quantified and much lower fatigue lives are measured after ageing. At a higher level flume tank tests have been performed on three-blade...
Tipo: Text Palavras-chave: Composite; Fatigue; Ageing; Tidal turbine; Flume tank; Finite-element model.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00079/19053/20068.pdf
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Experimental analysis of the floor inclination effect on the turbulent wake developing behind a wall mounted cube ArchiMer
Ikhennicheu, Maria; Gaurier, Benoit; Druault, Philippe; Germain, Gregory.
The present study aims at investigating turbulence characteristics in high flow velocity areas like those suitable for marine energy application. The Reynolds number, based on the rugosity height and mean flow velocity, is rather high: . For that purpose, experiments are carried out in a flume tank with as high as achievable in Froude similitude (in the tank: and ). Obstacles are canonical wall-mounted elements chosen to be representative of averaged bathymetric variations: a cube and a cube followed by an inclined floor. First, the wake topology past a canonical wall-mounted cube is illustrated from PIV measurements. Results show a flow behaviour already observed in the literature but for different upstream conditions ( and turbulence intensity). Second,...
Tipo: Text Palavras-chave: Turbulence; Experimental trials; Wall-mounted obstacles; PIV; POD; Quadrant method.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00449/56050/57570.pdf
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Experimental analysis of the wake past wide wall-mounted obstacles ArchiMer
Ikhennicheu, Maria; Germain, Gregory; Druault, Philippe; Gaurier, Benoit.
In high flow velocity areas like those suitable for marine energy application, bathymetry variations create strong velocity fluctuations in the water column. It is therefore essential to characterize the turbulence evolution in the wake of seabed elements which may impact the loads on tidal turbines. For that purpose, experiments are carried out in a flume tank in Froude similitude with a Reynolds number as high as achievable (Fr = 0.23 and Re = 2.5×10 5 ). The study focuses on large aspect ratio floor variations represented with a square wall-mounted cylinder of aspect ratio 6. The addition of a cube upstream of the cylinder is investigated. The cube impact on the wake development is larger than the side effects. Large scale turbulent events produced in...
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Ano: 2018 URL: https://archimer.ifremer.fr/doc/00482/59336/62114.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 and numerical results on VIV and WIO ArchiMer
Gaurier, Benoit; Germain, Gregory; Le Boulluec, Marc; Giry, Eric; Fontaine, Emmanuel.
Vortex-Induced Vibrations (VIV) are well-known and related to the majority of cylindrical structures subjected to strong winds or currents. The VIV limit the lifetime of the structure because they increase the forces and so the fatigue. When several structures of this kind are put together in close interaction, the wake effects (Wake Induced Oscillations - WIO) sometimes involve strong instabilities. If these structures are flexible or mobile, oscillations of several diameters can be observed and collisions can occur ([4] & [6]). Such structures are widespread in the oil industry where the extraction of oil in deep water can be done by means of risers. In some cases, risers are connected to a floating support called FPSO (Floating Production Storage...
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Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/publication-6584.pdf
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Experimental study of bubble sweep-down in wave and current circulating tank: Part I—Experimental set-up and observed phenomena ArchiMer
Delacroix, Sylvain; Germain, Gregory; Gaurier, Benoit; Billard, Jean-yves.
Bubble sweep-down is a significant issue for the oceanographic vessels, which affect the acoustic surveys. Experimental trials, carried out in the Ifremer wave and current circulating tank on a 1/30 model of the Pourquoi pas?, are presented. The results demonstrate that this kind of experimental facility is well suited to study the phenomenon of bubble sweep-down encountered around the bow of a ship under specific conditions. From these results, two kinds of bubble clouds formation have been observed and analysed: bubble clouds generated by vortex shedding and breaking waves. The vortex shedding bubble clouds appear randomly in all the configurations tested, even without waves or motions. This phenomenon is due to the interaction between the turbulent flow...
Tipo: Text Palavras-chave: Bubble sweep-down; Experimental trials; Ship motions; Bow waves.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00335/44578/44315.pdf
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