Development of an Acoustics of Bubbly Flows in a High Void Fraction by Integrating Inhomogeneous Theory of Sound Speed and Venturi-Tube Experiment

2018 Fiscal Year Final Research Report

• Project/Area Number: 16K18008
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Fluid engineering
• Research Institution: University of Tsukuba
• Principal Investigator: KANAGAWA Tetsuya 筑波大学, システム情報系, 助教 (80726307)
• Project Period (FY): 2016-04-01 – 2019-03-31
• Keywords: 音速 / ボイド率 / 気泡流 / 圧力波 / ソリトン / 衝撃波 / 非線形波動 / 非線形音響学

Outline of Final Research Achievements

A large difference between theoretical and experimental values of speed of sound in bubbly flows in a high void fraction should be corrected. The purpose of this study is to improve this difference by integrating a theory and an experiment. The main results are as follows: (i) The observation of bubble collapse, and the measurement of speed of sound and the pressure distribution, were experimentally performed; (ii) Nonlinear wave equations were theoretically derived especially focusing on a wave dissipation effect and a nonuniform distribution of flow velocity; (iii) The pressure distribution and the speed of sound were numerically predicted by solving the above-mentioned nonlinear wave equations; (iv) Theoretical and numerical values almost coincided with experimental values.

Free Research Field

流体力学, 非線形波動

Academic Significance and Societal Importance of the Research Achievements

気泡を含む水の流れの研究において，気体の占める割合は1 %程度に小さいことが当たり前であったが，泡の有効活用を目指す観点からは，沢山の泡を含む「高濃度気泡流」に挑む必要がある。しかし，10 %を超える高濃度の場合，音速の理論予測値と実験事実の間に大きな乖離があった。本研究は，厳密な数学的理論解析と精密な計測を適切に組み合わせて，上記乖離の原因を指摘すると同時に，乖離の多くの解消に成功した。