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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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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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