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ISSN オンライン: 2642-0554

EXPERIMENTAL STUDY ON DRAG REDUCTION BY MICROBUBBLES USING A 50M-LONG FLAT PLATE SHIP

Takahito Takahashi
Center for Smart Control of Turbulence, National Maritime Research Institute Shinkawa, Mitaka, Tokyo 181-0004, Japan

Akira Kakugawa
Ship Research Institute 6-38-1, Shinkawa, Mitaka Tokyo 181-0004, Japan

Yoshiaki Kodama
Ship Performance Division, National Maritime Research Institute 6-38-1 Shinkawa, Mitaka, Tokyo 181-0004, Japan

Masahiko Makino
Center for Smart Control of Turbulence, National Maritime Research Institute Shinkawa, Mitaka, Tokyo 181-0004, Japan

要約

Microbubble experiments were carried out in a 400m-long towing tank using a flat plate ship of up to 50m in length, aiming at its application to full-scale ships. The measured skin friction using skin friction sensors showed that the skin friction reduction persisted up to the downstream end of the 50m-long ship. The local void ratio distribution across the boundary layer was measured using a suction tube method, and it was found that the local void ratio close to the wall had strong correlation with skin friction reduction. Bubbles were injected at two different streamwise positions, in order to find out the effect of the boundary layer thickness on the skin friction reduction. It was found out that the distance from the injection point was dominant and that the boundary layer thickness had little effect.