2022 Fiscal Year Final Research Report
Investigation of Mechanism and Condition on Cavitation Threshold in High-Speed Water Flow by EFD-CFD-Bubble Dynamics Combination
| Project/Area Number |
20K04296
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Multi-year Fund |
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| Section | 一般 |
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| Review Section |
Basic Section 19010:Fluid engineering-related
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| Research Institution | Miyakonojo National College of Technology |
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Principal Investigator |
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| Project Period (FY) |
2020-04-01 – 2023-03-31
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| Keywords | 非循環型キャビテーションタンネル / キャビテーション流れのCFD解析 / 気泡力学 / 気泡核成長の動的閾値理論 / 張力 |
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| Outline of Final Research Achievements |
The present study clarifies dynamical threshold of a bubble nucleus in theoretical and experimental manners under tension induced in high-speed water flow within the narrow slit between the flat solid wall and the cylinder surface. The model equation of nucleus growth under tension is formulated based on Rayleigh-Plesset equation, resulting in dynamical threshold of cavitation. The result is ascertained to be reasonable compared with the growth of the nucleus in turbulent water flows by CFD simulation where nonequilibrium evaporation and heat conduction through the nucleus wall, and wall pressure reduction due to the translational motion of the nucleus traced by Lagrangian technique. Consequently, Blake’s threshold (static threshold) is found to be the necessary condition for cavitation whilst the dynamical one is the sufficient one.
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| Free Research Field |
流体工学
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| Academic Significance and Societal Importance of the Research Achievements |
① 高速水流中の円柱表面近傍で局所的な張力により単一気泡核が成長する場合，単一気泡核の並進運動をラグランジュ的に追跡し，気泡壁での非平衡蒸発，熱伝導，並進減圧を考慮してRayleigh-Plessetの式により気泡核の成長を解析，その結果を実験と比較して気泡核成長の動的閾値（張力，持続時間，気泡核半径の関係）を解明した（学術的意義）．
② 本報告者らが提案した動的閾値は流体機器内のキャビテーションのみならず，キャビテーションを利用したディーゼルエンジンの燃料霧化，水中ウォータージェット，水処理などにおいてもノズル設計に係る有用な成果である（社会的意義）．
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