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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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| 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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| 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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