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| Registros recuperados: 58 | |
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| 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... |
| Tipo: Text |
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| Ano: 2008 |
URL: http://archimer.ifremer.fr/doc/2008/publication-6584.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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| 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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| Marty, Antoine; Germain, Gregory; Facq, Jean-valery; Gaurier, Benoit; Damblans, Guillaume; Germain, Nicolas; Harris, Jeffrey; Maison, Antoine; Peyrard, Christophe; Relun, Nicolas. |
| Submarine cable behaviour is experimentally studied in the frame of the France Energies Marines project STHYF. In order to evaluate on-bottom stability of cables placed on rocky seabed with high roughness and submitted to combined wave and strong current, hydrodynamic loads are measured on a fixed slender cylinder closely fixed to a horizontal plate, with or without large roughness. A specified set of load cases (forced oscillations, current, forced oscillation + current) is considered to assess the hydrodynamic loads acting on the cylinder placed near a wall for varying gap-to-diameter ratios. The roughness effects on cylinder loads and on the flow are studied in detail. The result show a significant difference between rough and smooth bottom... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00660/77244/78696.pdf |
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| 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... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00482/59336/62114.pdf |
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| Medina, Olmo Duran; Schmitt, Francois G.; Calif, Rudy; Germain, Gregory; Gaurier, Benoit. |
| The correlation between the flow turbulence and the performances of a marine current turbine is studied. First, the incoming flow encountered in the flume tank is characterized in the framework of fully developed turbulent cascades in the inertial range. The Reynolds number, the Kolmogorov dissipation scale and the integral scale, are estimated from flow measurements. The intermittency of the turbulence is characterized in the lognormal multifractal framework, and the influence of the turbulent flow on the turbine power is assessed. The rotor speed control unit characteristics used for the turbine regulation induces non-negligible effects on the turbine behavior under fluctuations loads. Even if the power spectrum does not reveal any scale invariance, a... |
| Tipo: Text |
Palavras-chave: Marine energy; Turbulence; Multifractal energy cascade; Intermittency; Turbine power production; High frequency data rate. |
| Ano: 2017 |
URL: http://archimer.ifremer.fr/doc/00385/49620/50134.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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| Mallat, Bachar; Germain, Gregory; Billard, Jy; Gaurier, Benoit; Facq, Jean-valery; Bacchetti, Thomas. |
| The bubble sweep-down phenomenon around oceanographic research vessels generates acoustic disturbances. This phenomenon has affected the acoustic surveys for many years and is still a significant issue. The reason is that neither towing tank trials nor numerical simulations are able to properly address this phenomenon. We proposed a specific experimental protocol in a wave and current circulating tank allowing a 3D visualization of the bubble sweep-down phenomenon around two ship models with different bow geometries. Visualisations and Particle Image Velocimetry (PIV) measurement results both obtained in the bow vicinity of the two ship models are presented in this paper. These results allow a better representation of the phenomenon compare to previous... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00412/52332/53117.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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| Marty, Antoine; Berhault, Christian; Damblans, Guillaume; Facq, Jean-valery; Gaurier, Benoit; Germain, Gregory; Soulard, Thomas; Schoefs, Franck. |
| This document describes the experimental set-up of OMDYN2 and LEHERO-MG projects. The study aims to quantify the impact of biofouling on the dynamic behaviour of an underwater power cable by analysing the hydrodynamic coefficients, such as drag and added mass coefficients. Experiments have been carried out in the wave and current basin of IFREMER, located at Boulogne-sur-mer, in order to compare the dynamics of several cylinders with or without roughness. Three cylinders are tested, two cylinders with different roughnesses and one smooth cylinder. The studied roughnesses concern realistic marine growth and have therefore significantly bigger dimensions (like mussels) than roughness studied in the research literature on the subject. Tests are conducted... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00660/77245/78697.pdf |
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| 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 with Re as high as achievable in Froude similitude, with bathymetry variations experimentally represented with various wall-mounted square elements of height H: a cylinder or a cube as unitary obstacles and combinations of these elements followed by an inclined floor to resemble smooth bathymetry changes. The onset flow is a simple boundary layer profile with height 1.3 H and a low turbulence... |
| Tipo: Text |
Palavras-chave: Turbulence; Experimental trials; Wall-mounted obstacles; PIV; LDV; Marine energy. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00502/61356/64997.pdf |
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| Mycek, Paul; Gaurier, Benoit; Germain, Gregory; Pinon, Gregory; Rivoalen, Elie. |
| The future implantation of second generation marine current turbine arrays depends on the understanding of the negative interaction effects that exist between turbines in close proximity. This is especially the case when the turbines are axially aligned one behind another in the flow. In order to highlight these interaction effects, experiments were performed in a flume tank on 3-bladed 1/30th scale prototypes of horizontal axis turbines. This work focuses on the interactions between two horizontal axis marine current turbines, axially aligned with the upstream flow. Thrust and power coefficients function of the rotation speed of the downstream device are presented. Besides, the wake of each turbine is characterised so as to explain their behaviour. A... |
| Tipo: Text |
Palavras-chave: Marine current turbine; Performance; Wake; Turbulence; Array; Tidal turbine. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00175/28644/27110.pdf |
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| Carlier, Clement; Fur, Arnaud; Pinon, G; Gaurier, Benoit; Germain, Gregory; Rivoalen, E. |
| Le developpement de fermes d'hydroliennes est un sujet de recherche actif depuis quelques annees. Cependant, des etudes sont encore necessaire pour comprendre le comportement de tels parcs. Un des sujets porte sur l'influence de la turbulence ambiante sur les machines. Des etudes recentes ont ainsi montre que le taux de turbulence ambiant d'un ecoulement modifiait enormement le comportement des turbines. En consequence, les simulations numeriques se doivent de reproduire l'effet de la turbulence ambiante, du moins son influence sur les performances et sur le sillage des turbines. Ce papier presente les derniers developpements numeriques realises dans le but de prendre en compte les effets de la turbulence ambiante sur le comportement d'hydroliennes a axe... |
| Tipo: Text |
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| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00367/47868/47865.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; Gaurier, Benoit; Billard, Jean-yves. |
| In this second part, images acquired from the specific trials developed in order to study the phenomenon of bubble sweep-down are analysed. A post-processing method has been developed to analyse the two air entrainment mechanisms described in the first part, for several test configurations. Bubble clouds are described in terms of depth, area and velocity for both vortex shedding and breaking wave bubble clouds. A parametric study is also performed to calculate the influence of each test parameter on the frequency of bubble generation. It is demonstrated that the occurrence of bubble clouds is proportional to the wave height, with a considerable influence of the phase shift between waves and motions. The overall results provide new elements for the... |
| Tipo: Text |
Palavras-chave: Bubble sweep-down; Experimental trials; Ship motions; Bow waves. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00335/44577/44314.pdf |
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| Registros recuperados: 58 | |
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