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Caractérisation de la génération et de la propagation de bulles autour de la carène des navires scientifiques

Abstract : One of the main assignments of Ifremer is to study the seabed and the resources undersea, through a large oceanographic fleet used across the globe. For that purpose, ships are equipped with different kinds of SONAR (SOund Navigation And Ranging) to obtain the information sought in the water column. In some sea conditions, waves and ship motions generate significant air entrainment below the surface. Bubble clouds are then carried under the hull by the flow. The interaction between these bubbles and the acoustic waves may result in data loss, and therefore in a considerable reduction of the vessel’s productivity. The tools used to study this phenomenon are currently limited : the numerical models are not efficient enough to simulate at a time air entrainment at the bow and the two phase flow around the hull. On the other hand conventional towing tank tests are not entirely satisfactory. During this PhD research work, a specific test method to study this phenomenon has been developed and implemented at the Ifremer wave and current tank. This method requires the synchronization between a wave generator and a movement generator (hexapod) that enables to force the model motions, calculated in advance by numerical simulations. With this configuration, the effects of waves or motions characteristics on the bubbles generation can be studied independently. A complete instrumentation allowed to acquire images sequences to characterize the air entrainment at the bow of the model. Two distinct mechanisms have been observed : the generation of bubbles by vortex shedding or by the breaking bow wave. A post-processing method has been developed to analyse these mechanisms, for many test configurations. A parametric study was performed to calculate the frequency of bubbles generation for each test parameter. PIV measurements allowed to correlate the dynamic of bubbles clouds with the own flow dynamic. The overall results provide new elements for the understanding and the study of the phenomenon, with the final objective of obtaining a reliable tool that facilitates the design of research vessels.
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Submitted on : Thursday, July 11, 2019 - 5:02:07 PM
Last modification on : Friday, July 17, 2020 - 2:53:53 PM


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  • HAL Id : tel-02180918, version 1


Sylvain Delacroix. Caractérisation de la génération et de la propagation de bulles autour de la carène des navires scientifiques. Mécanique des fluides [physics.class-ph]. Université de Bretagne occidentale - Brest, 2015. Français. ⟨NNT : 2015BRES0014⟩. ⟨tel-02180918⟩



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