A 3D study of the bubble sweep-down phenomenon around a 1/30 scale ship model

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 that the bubble clouds are propagated in the flow direction with a horizontal expansion which is non negligeable, reaching a close position to the hull. The overall results provide new elements for the study and the understanding of the phenomenon compared with previous 2D studies.