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| Registros recuperados: 58 | |
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| 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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| 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 |
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| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00252/36293/34822.pdf |
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| 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... |
| Tipo: Text |
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| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00389/50002/50587.pdf |
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| 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 |
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| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00022/13359/10388.pdf |
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| 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... |
| Tipo: Text |
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| Ano: 2007 |
URL: http://archimer.ifremer.fr/doc/00023/13439/10447.pdf |
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| 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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| 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. |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00247/35806/34320.pdf |
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| Magnier, Maelys; Druault, Philippe; Gaurier, Benoit; Germain, Gregory; Ifremer; Sorbonne Universités. |
| Areas with strong tidal currents that can be exploited with tidal turbines often have complex bathymetries where the turbulent intensity of these currents can reach very high values. To study the effects of bathymetric variations on the operation of a tidal turbine, an experimental device has been developed in the Ifremer circulation basin. The wake of two kinds of bathymetries, a cylinder with a square base and a cube followed by this same cylinder, are characterized and compared from PIV measurement results. The results show that the wake of the cylinder is more energetic than that of the tandem configuration. The vortex structures that it emits rise to the surface unlike those resulting from the tandem, the cube preventing their development. The effects... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00660/77243/78695.pdf |
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| 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 |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00141/25200/23360.pdf |
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| 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,... |
| Tipo: Text |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00247/35821/34349.pdf |
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| 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 |
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| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00247/35807/34321.pdf |
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| 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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| 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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| 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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| Gaurier, Benoit; Druault, Ph.; Ikhennicheu, Maria; Germain, Gregory. |
| In the main tidal energy sites like Alderney Race, turbulence intensity is high and velocity fluctuations may have a significant impact on marine turbines. To understand such phenomena better, a three-bladed turbine model is positioned in the wake of a generic wall-mounted obstacle, representative of in situ bathymetric variation. From two-dimensional Particle Image Velocimetry planes, the time-averaged velocity in the wake of the obstacle is reconstructed in the three-dimensional space. The reconstruction method is based on Proper Orthogonal Decomposition and enables access to a representation of the mean flow field and the associated shear. Then, the effect of the velocity gradient is observed on the turbine blade root force, for four turbine locations... |
| Tipo: Text |
Palavras-chave: Tidal turbine; Blade force; Turbulent wake; Experimental trials; PIV; POD. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00643/75535/76540.pdf |
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| Registros recuperados: 58 | |
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