Bulles Navire

Bubble generation by wave breaking and body-wave interaction is a source of diverse interest. For naval ships, this kind of bubbles generates underwater sound and a wake visible far behind the ship. In the particular case of research vessels, bubble generation must be avoided to reduce the degradation of acoustic equipment performances. Indeed, in bad weather conditions, the ship bow wave generates a significant aeration carried out by the flow under sonar locations. This phenomenon of bubble sweep-down must be prevented as much as possible in order to ensure high quality acoustic surveys, even if today there are no experimental and numerical tools allowing the exact reproduction of bubble generation by a ship's bow under waves and motions. Ifremer have launched a research program, based on PhD works [1 ; 2], for the better knowledge of this specific diphasic phenomenon. The obtained results have been valorized through several scientific papers :

• an in-situ study for the characterization of 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?
  Bubble sweep-down occurrence characterization on Research Vessels. Delacroix Sylvain, Germain Gregory, Berger Laurent, Billard Jean-Yves (2016). Ocean Engineering, 111, 34-42. Publisher's official version : https://doi.org/10.1016/j.oceaneng.2015.10.040 

• an experimental modeling of the phenomenon in the Ifremer wave and current circulating tank on a 1/30 model of the Pourquoi pas? In order to observe the bubble clouds dynamic
  Experimental study of bubble sweep-down in wave and current circulating tank. Delacroix Sylvain, Germain Gregory, Gaurier Benoit, Billard Jean-Yves (2016)
  • Part I—Experimental set-up and observed phenomena. Ocean Engineering, 120, 78-87. Publisher's official version : https://doi.org/10.1016/j.oceaneng.2016.05.003
  • Part II—Bubble clouds characterization. Ocean Engineering, 120, 88-99. Publisher's official version : https://doi.org/10.1016/j.oceaneng.2016.05.008

• some specific developments in order to improve the PIV measurements analysis and the description of the bubble sweep-down phenomenon
  • Automatic dynamic mask extraction for PIV images containing an unsteady interface, bubbles, and a moving structure. Dussol David, Druault Philippe, Mallat Bachar, Delacroix Sylvain, Germain Gregory (2016).
    Comptes Rendus Mecanique, 344(7), 464-478. Publisher's official version : https://doi.org/10.1016/j.crme.2016.03.005
  • Breaking wave bubble measurements around ship model by optical probe. Khaddaj-Mallat Bachar, Germain Gregory, Billard Jean-Yves, Gabillet Céline (2022).
    Ocean Engineering, 246, 110438 (12p.)

• the comparison of three kinds of bow shape on the bubble clouds occurrence and a 3D study for bubble cloud characterisation
  • Experimental study of the bubble sweep-down phenomenon on three bow designs.  Mallat Bachar, Germain Gregory, Gaurier Benoit, Druault Philippe, Billard Jean-Yves (2018)
    Ocean Engineering, 148, 361-375. Publisher's official version : https://doi.org/10.1016/j.oceaneng.2017.11.041
  • A 3D study of the bubble sweep-down phenomenon around a 1/30 scale ship model. Mallat Bachar, Germain Gregory, Billard Jean-Yves, Gaurier Benoit (2018)
    European Journal Of Mechanics B-fluids, 72, 471-484. Publisher's official version : https://doi.org/10.1016/j.euromechflu.2018.07.014

Even if this work does not allow to answer to the entire problematic, the experimental setup developped here forms a reliable tool that simplifies the design research vessels. This setup has been used for the BHO2M design built by PIRIOU.

[1] Delacroix Sylvain (2015). Caractérisation de la génération et de la propagation de bulles autour de la carène des navires scientifiques. PhD Thesis, Université de Bretagne Occidentale (Financement DGA, Ifremer).
[2] Khaddaj-Mallat Bachar (2017). Etude du phénomène d’aération sur les carènes des navires océanographiques, PhD Thesis, Université de Lille (financement Région Haut de France/Ifremer).