Development of three-dimensional flow field measurement method for bubbly flow using light-field camera

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K14975
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 24020:Marine engineering-related
• Research Institution: National Institute of Maritime, Port and Aviation Technology
• Principal Investigator: Hiroi Takamichi 国立研究開発法人海上・港湾・航空技術研究所, その他部局等, 研究員 (60734233)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: PIV / 気液二相流 / 摩擦抵抗低減

Outline of Final Research Achievements

The objective of this study was to develop a three-dimensional flow field measurement technique (LF-PIV) of bubble flow using a light field camera to reveal the vortex structure around sub-millimeter bubbles. Since LF-PIV could not be realized due to technical issues, a two-dimensional PTV/shadowgraphy system developed for validation was used to measure bubbles and ambient flow fields for velocity changes in the flow path. As a result, it was found that the suppression of wall turbulent eddies and the generation of isotropic turbulent eddies, which contribute to drag reduction by bubbles, occur regardless of the bubble diameter, but that when the bubble diameter is large, buoyancy forces cause the bubble interface to advect near the wall surface at a high speed, generating eddies and increasing drag. This clarifies the basic structure of frictional resistance, which changes as the bubble diameter changes and the bubble distribution changes.

Free Research Field

船舶海洋工学

Academic Significance and Societal Importance of the Research Achievements

本研究では、気泡による摩擦抵抗変化の速度影響の基本構造が明らかになった。気泡による抵抗低減現象においては、実験装置による抵抗低減効果の違いを説明することが出来ていなかったが、本研究の成果により本現象の統一的解釈が進むものと考えられる。また、本成果はシミュレーションの高度化にも寄与し、本現象を利用した空気潤滑船の性能向上にも資するものである。