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| Registros recuperados: 23 | |
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| Bouhoubeiny, Elkhadim; Germain, Gregory; Druault, Philippe. |
| Flow field measurements behind a rigid cod-end and a moving bottom trawl are conducted using Time Resolved PIV method. This method is based on an image acquisition rate allowing the time resolved sampling of the vortex shedding phenomenon. Based on such measurements, the main flow characteristics around fishing net structure are investigated. Moreover, the vortex shedding frequency phenomenon associated with both the rigid cod-end and the moving bottom trawl is analyzed. We then present the analysis of the instability of the shear layer separating a moving trawl having 3 degrees of freedom. Using also the Proper Orthogonal Decomposition (POD) for such investigation, it is demonstrated the effectiveness of this procedure to extract not only the large scale... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00022/13280/10324.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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| Druault, Philippe; Germain, Gregory. |
| The coupled dynamics of the codend fluttering motion and its hydrodynamics behavior are investigated based on PIV measurements carried out around a 1/10 scaled model codend. The mean wake flow characteristics are firstly analyzed demonstrating the great effect of the codend motion. The differences in flow contour between fluttering motion and no-fluttering codend are highlighted by analyzing the classical mean characteristics of a body wake flow. In presence of fluttering motion, the classical results are recovered only if one considers the vertical extent of the codends oscillations as a reference length scale. Secondly, the frequency content of codend oscillations is analyzed and it is linked to the physical mechanisms. It is observed that the motion of... |
| Tipo: Text |
Palavras-chave: PIV measurements; Fishing net structure; Wake hydrodynamics; Fluttering structure. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00344/45503/45055.pdf |
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| Bouhoubeiny, Elkhadim; Druault, Philippe; Germain, Gregory. |
| Time-Resolved Particle Image Velocimetry (PIV) measurements are performed to investigate the hydrodynamic flow interaction with a representative piece of fishing net structure. Using the advanced post-processing mathematical tool based on Proper Orthogonal Decomposition, the phase averaged mean properties of turbulent flows are extracted from PIV database, demonstrating the existence of a Turbulent Boundary Layer (TBL) flow developing all around the sheet of net. The results also show that the mesh opening and so the turbulent flow passing through the structure are strongly influenced by the structure oscillations. This work allows us to demonstrate that the drag computation of fishing gear, commonly based on uniform velocity, needs to consider not only... |
| Tipo: Text |
Palavras-chave: Fishing net structure; Hydrodynamics; PIV; Turbulent boundary layer flow. |
| Ano: 2014 |
URL: http://archimer.ifremer.fr/doc/00184/29552/27878.pdf |
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| Druault, Philippe; Germain, Gregory; Facq, Jean-valery. |
| To gain a better understanding of the fluid–structure interaction and especially when dealing with a flow around an arbitrarily moving body, it is essential to develop measurement tools enabling the instantaneous detection of moving deformable interface during the flow measurements. A particularly useful application is the determination of unsteady turbulent flow velocity field around a moving porous fishing net structure which is of great interest for selectivity and also for the numerical code validation which needs a realistic database. To do this, a representative piece of fishing net structure is used to investigate both the Turbulent Boundary Layer (TBL) developing over the horizontal porous moving fishing net structure and the turbulent flow passing... |
| Tipo: Text |
Palavras-chave: Unsteady turbulent flow; Particle Image Velocimetry; Oscillating structure; Fishing structure. |
| Ano: 2015 |
URL: http://archimer.ifremer.fr/doc/00271/38216/36479.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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| Bouhoubeiny, Elkhadim; Druault, Philippe. |
| To enhance the temporal resolution of the PIV measurements of pseudo-periodic turbulent flows, Proper Orthogonal Decomposition (POD) has been previously used to time interpolate PIV database. In this note, it is demonstrated that such POD interpolation is equivalent to the classical mathematical interpolation when dealing with the whole POD eigenfunctions, since POD is a linear transform. In fact, the POD-based time interpolation is only valid for the large scale structures of the flow. The advantage of using POD procedure resides in its efficiency in extracting the dominant flow structures. In this sense, other interpolation methods such as turbulent filtering procedures could provide similar results. To cite this article: E. Bouhoubeiny, P Druault, C R.... |
| Tipo: Text |
Palavras-chave: Fluid mechanics; Particle image velocimetry; Proper orthogonal decomposition; Large scale flow structures. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00021/13199/10314.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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| Germain, Gregory; Priour, Daniel; Vincent, Benoit; Billard, Jean-yves; Druault, Philippe; Bouhoubeiny, Elkhadim; Alexandrini, Bertrand; Le Touze, David; Khaled, Ramez; Mnassri, Ilyes. |
| Le comportement hydrodynamique des structures poreuses utilisées pour la pêche (chaluts, nasses, cages, seines) est aujourd’hui encore mal connu. Les chaluts étant responsables de la plus grosse part de la consommation de fuel en action de pêche, ce projet a pour objectif de développer un outil de conception de chalut permettant de réduire au maximum la traînée de l’engin.L’outil ainsi développé devrait permettre d’obtenir un gain de l’ordre de 20% sur la traînée d’un chalut, tout en conservant une efficacité en pêche comparable. Les développements réalisés pourront également être étendus pour étudier les différents types de structures poreuses utilisées pour la pêche et mieux appréhender le développement de dispositifs de sélectivité. |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00116/22716/20683.pdf |
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| Bouhoubeiny, Elkhadim; Germain, Gregory; Druault, Philippe. |
| Flow field measurements past a fixed rigid cod-end structure and past a porous fishing net structure are conducted using Time-Resolved PIV method. The rigid cod-end is first used to characterize finely the wake flow. Proper Orthogonal Decomposition (POD) is then applied in order to extract the large scale energetic vortices of the flow from the measured velocity field. It is then observed that the first POD modes are associated to the Karman's type flow structure of vortex shedding. It is shown that the characteristics of the wake flow behind the rigid cod-end flow configuration compare quite well with previous ones obtained from bluff cylinder or sphere wake analyzes. Second, PIV measurements are performed around a non-rigid bottom trawl which is free to... |
| Tipo: Text |
Palavras-chave: Fishing gear; PIV measurements; Vortex shedding; Proper Orthogonal Decomposition. |
| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00027/13820/11046.pdf |
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| Dussol, David; Druault, Philippe; Mallat, Bachar; Delacroix, Sylvain; Germain, Gregory. |
| When performing Particle Image Velocimetry (PIV) measurements in complex fluid flows with moving interfaces and a two-phase flow, it is necessary to develop a mask to remove non-physical measurements. This is the case when studying, for example, the complex bubble sweep-down phenomenon observed in oceanographic research vessels. Indeed, in such a configuration, the presence of an unsteady free surface, of a solid–liquid interface and of bubbles in the PIV frame, leads to generate numerous laser reflections and therefore spurious velocity vectors. In this note, an image masking process is developed to successively identify the boundaries of the ship and the free surface interface. As the presence of the solid hull surface induces laser reflections, the hull... |
| Tipo: Text |
Palavras-chave: Particle image velocimetry; Unsteady free interface; Edge detection method; Morphological analysis. |
| Ano: 2016 |
URL: http://archimer.ifremer.fr/doc/00327/43778/43335.pdf |
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| Ikhennicheu, Maria; Germain, Gregory; Druault, Philippe; Gaurier, Benoit. |
| In high flow velocity areas like those suitable for tidal applications, turbulence intensity is high and flow variations may have a major impact on tidal turbines behaviour. Large boils that can be observed at the sea surface are emitted from the sea floor and may interact with the tidal turbines. These boils have then to be characterized. The Reynolds number, based on the rugosity height and the mean flow velocity, is rather high in this context: Re ¼ 2:5 107. For that purpose, experiments are carried out in a flume tank with Re as high as achievable in Froude similitude (in the tank: Re ¼ 2:5 105 and Fr ¼ 0:23) in order to study coherent flow structures emitted behind seabed obstacles. The obstacle is here a canonical square wall-mounted cylinder chosen... |
| Tipo: Text |
Palavras-chave: Turbulence; Experimental trials; Wall-mounted cylinder; PIV; LDV; POD; Lamb-Oseen. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00494/60527/64189.pdf |
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| Gaurier, Benoit; Ikhennicheu, Maria; Druault, Philippe; Germain, Gregory; Facq, Jean-valery; Pinon, Grégory. |
| In high flow velocity areas like those suitable for marine energy application, bathymetry variations create strong velocity fluctuations in the water column. Experiments showed that wide cylindrical obstacles generate large velocity fluctuations, like those measured at sea. In order to study the effects of these fluctuations on the turbine behaviour, an experimental set-up has been developed in the circulating tank of Ifremer in Boulogne-sur-mer by positioning a cylinder and a turbine in its wake. Simultaneous PIV measurements give access to the flow velocity upstream of the turbine. Velocity and efforts are compared in terms of cross-correlation, coherence and their spectral content is studied. Results show that the turbine loads follow velocity... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00482/59334/62112.pdf |
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| Mercier, Philippe; Ikhennicheu, Maria; Guillou, Sylvain; Germain, Gregory; Poizot, Emmanuel; Grondeau, Mikaël; Thiébot, Jérôme; Druault, Philippe. |
| Flows at tidal-stream energy sites are characterised by high turbulence intensities and by the occurrence of highly energetic large and coherent flow structures. The interaction of the flow with seabed roughness is suspected to play a major role in the generation of such coherent flow structures. The problem is introduced with canonical wall-mounted square obstacles representing abrupt changes of bathymetry, with high Reynolds number flow (Re = 250000). Two methods are used: a numerical model, based on the LBM (Lattice Boltzmann Method) combined with LES (Large Eddy Simulation) and an experimental set-up in a circulating tank. The numerical model is validated by comparison with experimental data. In the case of a wall-mounted square cylinder, large-scale... |
| Tipo: Text |
Palavras-chave: Turbulence; Coherent flow structure; Numerical simulation; Lattice Boltzmann Method; Large Eddy Simulation; Wall-mounted obstacles. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00617/72940/72147.pdf |
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| Bouhoubeiny, Elkhadim; Germain, Gregory; Druault, Philippe. |
| The work presented in this paper is carried out under the HydroPêche project with the aim to develop a tool for an automatic optimisation of trawl in order to minimize the drag of the gear. One of the aspects of this project is the experimental investigation of the turbulent flow around bottom trawls. For that purpose, Particle Image Velocimetry measurements in a flume tank are implemented to access to the two-dimensional velocity field around a bottom trawl. Having an important experimental database allows not only the calibration of numerical models aiming at simulating the flow around a fishing net but also the validation of numerical simulation results. Such experimental technique has the advantage in accessing the turbulent flow field and then allows... |
| Tipo: Text |
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| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00021/13268/10315.pdf |
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| Druault, Philippe; Bouhoubeiny, Elkhadim; Germain, Gregory. |
| Particle image velocimetry (PIV) measurements are made to investigate the boundary layer developing over a modeled bottom trawl. The random motion of the fishing net structure as well as the flexibility and the porosity of this structure means that it is not enable to access the main characteristics of such a flow, using classical post-processing mathematical tools. An innovative post-treatment tool based on proper orthogonal decomposition (POD) is then developed to extract the mean velocity flow field from each available PIV instantaneous unsteady velocity field. In order to do so, the whole available velocity database is used to compute POD eigenfunctions and the first POD modes are identified as representing the mean flow field. It is then possible to... |
| Tipo: Text |
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| Ano: 2012 |
URL: http://archimer.ifremer.fr/doc/00088/19935/17776.pdf |
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| Registros recuperados: 23 | |
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