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Registros recuperados: 11
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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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Bubble sweep-down occurrence characterization on Research Vessels ArchiMer
Delacroix, Sylvain; Germain, Gregory; Berger, Laurent; Billard, Jean-yves.
Bubble sweep-down on oceanographic vessels generates acoustic perturbations. We propose in this work to characterize the sub-surface bubbles occurrence conditions from acoustic data analysis acquired during surveys in relatively shallow water with the IFREMER research vessels Thalassa and Pourquoi Pas?. The methodology of data analysis used in this work allows us to characterize the sailing conditions influence on bubble sweep-down occurrence. The correlation between sailing conditions and acoustic perturbations tends to demonstrate that the presence of bubbles under the hull is clearly related to the wind speed and natural aeration, and that surface bubbles are advected differently in the water column by the two vessels
Tipo: Text Palavras-chave: Bubble sweep-down; Acoustic perturbation; Ship motion.
Ano: 2016 URL: http://archimer.ifremer.fr/doc/00294/40557/39632.pdf
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Cable length optimization for trawl fuel consumption reduction ArchiMer
Khaled, Ramez; Priour, Daniel; Billard, Jean-yves.
A numerical method for optimization of the cable lengths in trawls with respect to the ratio between the estimated trawl drag and the predicted catch efficiency is developed and applied. The trawl cables of interest are warps, bridles, headline and footrope. The optimization algorithm applies an ordered sequential process changing one cable length at the time. It is assumed in the predictions that the catch efficiency of the trawl is proportional with the trawl mouth area. In a case study optimizing a bottom trawl used on a research vessel by applying the new method it is predicted that it would be possible to reduce the ratio between trawl drag and catch efficiency by up to 46% by optimizing the cable lengths. Thus this would enable a considerable...
Tipo: Text Palavras-chave: Bottom trawl; Modeling; Optimization; Fuel consumption; Drag; Swept area; Mouth surface; Fish distribution.
Ano: 2013 URL: http://archimer.ifremer.fr/doc/00130/24106/22857.pdf
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Compte rendu final d’exécution de l’opération dans le cadre du projet HydroPêche ArchiMer
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
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00116/22716/20683.pdf
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Couche limite dans le sillage d'une poche de cavitation ArchiMer
Billard, Jean-yves; Djeridi, Henda; Sarraf, Christophe.
The results of an experimental investigation of the turbulent boundary layer that develops on a symmetric hydrofoil at moderate Reynolds number when a stable partial cavity takes place in the vicinity of the leading edge at angle of attack of 10 degrees, are presented. The modifications of the mean and turbulent properties introduced by the e existence of the vapour phase have been compared to the same quantities in the non cavitating state. A particular focus has been put on the evolution of the logarithmic law of the velocity profile and on the modification of the global parameters The higher order moments have been studied to highlight the exchanges and transfers of turbulent quantities between the different regions of the boundary layer The results...
Tipo: Text
Ano: 2009 URL: http://archimer.ifremer.fr/doc/00000/11152/8349.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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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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Experimental study of bubble sweep-down in wave and current circulating tank: Part II—Bubble clouds characterization ArchiMer
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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Experimental study of the bubble sweep-down phenomenon on three bow designs ArchiMer
Mallat, Bachar; Germain, Gregory; Gaurier, Benoit; Druault, Philippe; Billard, Jean-yves.
The bubble sweep-down phenomenon around the oceanographic research vessels generates acoustic perturbations. A specific experimental protocol has been developed in a wave and circulating tank to study this phenomenon. This protocol is used to carry out trials on three different ship models in order to study the influence of the bow geometry on the bubble generation. For different test configurations, bubble clouds are described and compared in terms of area, maximal depth and vertical velocity to highlight bubble cloud dynamics surrounding the three ship models. The relation between the hydrodynamic flow field and the bubble generation is studied by means of Particle Image Velocimetry (PIV) measurements to study the phenomenon by the use of phase averaged...
Tipo: Text Palavras-chave: Bubble sweep-down; Experimental trials; Bow geometry; Bubble cloud dynamics; PIV.
Ano: 2018 URL: https://archimer.ifremer.fr/doc/00412/52329/53360.pdf
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HydroPêche : a way to improve energy efficiency of fishing devices ArchiMer
Germain, Gregory; Druault, Philippe; Lewandowski, Roger; Benoit, Vincent; Priour, Daniel; Billard, Jean-yves.
The project presented here and named HydroPêche aims to develop a tool for an Automatic optimisation of trawl in order to minimize the drag of the gear. For that purpose, different aspects are studied in order : a/ to extend the basis of experimental data on flow characteristics governing the hydrodynamic behaviour of different porous structures ; b/ to develop numerical tools to simulate more realistic flow around porous structures taking into account fluid / structure interactions; c/ to develop automatic optimisation tools to design efficient trawls in terms of energy consumption. The developed tool should provide a substantial gain on the fuel consumed of actual fishing devices while maintaining a comparable fishing efficiency. The developments made...
Tipo: Text
Ano: 2010 URL: http://archimer.ifremer.fr/doc/00021/13266/10313.pdf
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HydroPêche : experimental and numerical devlopments for fishing devices optimisation ArchiMer
Germain, Gregory; Bouhoubeiny, Elkhadim; Druault, Philippe; Priour, Daniel; Khaled, Ramez; Billard, Jean-yves; Vincent, Benoit; Mnassri, Ilyes.
The goal of HydroPêche project is to develop tools for trawl optimisation in order to minimize the drag of the gear. A work in three areas : extend the basis of experimental data on flow characteristics governing the hydrodynamic behaviour of different porous structures ; developp numerical tools to simulate more realistic flow around porous structures taking into account fluid / structure interactions ; develop optimisation tools to design efficient trawls in terms of energy consumption.
Tipo: Text
Ano: 2012 URL: http://archimer.ifremer.fr/doc/00141/25194/23304.pdf
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