Development of external two-phase flow prediction method applicable to seawater environment

2019 Fiscal Year Final Research Report

• Project/Area Number: 17H03487
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Naval and maritime engineering
• Research Institution: Tokyo University of Marine Science and Technology
• Principal Investigator: Hazuku Tatsuya 東京海洋大学, 学術研究院, 教授 (60334554)
• Co-Investigator(Kenkyū-buntansha): 井原 智則 東京海洋大学, 学術研究院, 助教 (70767350)
• Project Period (FY): 2017-04-01 – 2020-03-31
• Keywords: 船舶工学 / 空気潤滑法 / 気液二相流 / 外部流れ / 抵抗低減

Outline of Final Research Achievements

This study was aimed at developing a new analytical method for the external two-phase flow in the seawater, which contributes improvement of a ship drag reduction technology based on the air lubrication method.
The database on local flow structures in the external two-phase flow under a model ship bottom was newly constructed through the experiment using a circulation water tunnel. Experiments for a single bubble and bubbly flows in the seawater were also performed to identify the characteristics of the interfacial drag of a single bubble and the bubble coalescence in the seawater. Based on the obtained experimental data and the analytical results, a modeling of the external two-phase flow was examined by taking the bubble layer thickness as a length scale and a new correlation for predicting void fraction under the ship bottom was successfully developed.

Free Research Field

船舶・海洋工学

Academic Significance and Societal Importance of the Research Achievements

海水中および外部流れの二相流の局所流動構造に着目した研究は、国内外において類例がほとんどなく、その実験的、解析的研究を実施した本研究は、現状に鑑みて新規性が高い。本研究により、外部流れの二相流の流動機構と海水中の気泡挙動に関する新たな知見が得られ、さらに外部流れの二相流を対象とした新しいボイド率予測式が開発された。これらの成果は、これまで開発途上であった海水中および外部流れの二相流の解析技術を進展させるものであり、今後のさらなる研究の推進によって、空気潤滑法による船体抵抗低減技術の高度化が期待できる。