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Mechanism and performance of a hydrofoil bubble generator utilized for bubbly drag reduction ships

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Title: Mechanism and performance of a hydrofoil bubble generator utilized for bubbly drag reduction ships
Authors: Murai, Yuichi Browse this author →KAKEN DB
Sakamaki, Haruki Browse this author
Kumagai, Ichiro Browse this author
Park, Hyun Jin Browse this author
Tasaka, Yuji Browse this author →KAKEN DB
Keywords: Bubbly drag reduction
Hydrofoil bubble generator
Air lubrication
Two-phase flow
Issue Date: 15-Nov-2020
Publisher: Elsevier
Journal Title: Ocean Engineering
Volume: 216
Start Page: 108085
Publisher DOI: 10.1016/j.oceaneng.2020.108085
Abstract: Following the success of bubbly drag reduction for marine vessels by hydrofoil bubble generators (Kumagai et al., 2015), we conducted two kinds of experiments to specify and improve its working principle. Firstly, PIV measurement was carried out to elucidate the flow structure around a hydrofoil running beneath a free surface. Froude number dependence of the anti-stall characteristics and cancellation of vertical pressure gradient above the hydrofoil were confirmed, which entrain the atmospheric air into water flow. Secondly, we mounted the hydrofoil to a model ship that runs in a 100-m-towing facility and found three different two-phase flow patterns in realizing bubble generation. Volume flow rate of generated bubbles increased with the ship speed to the power of greater than two, thus wall-occupation fraction of bubbles also increases with the ship speed. Furthermore, hydrofoil drag during bubble generation was measured and used to estimate net power-saving, having proved advantage of the hydrofoil bubble generator for long ships at high speed conditions.
Rights: © <2020>. This manuscript version is made available under the CC-BY-NC-ND 4.0 license
Type: article (author version)
Appears in Collections:工学院・工学研究院 (Graduate School of Engineering / Faculty of Engineering) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 村井 祐一

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