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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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Automatic dynamic mask extraction for PIV images containing an unsteady interface, bubbles, and a moving structure ArchiMer
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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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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Visualisation 3D du phénomène de bullage autour de deux modèles d’étraves ArchiMer
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...
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Ano: 2016 URL: http://archimer.ifremer.fr/doc/00412/52332/53117.pdf
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