An experimental study using linear modes as breakthroughs in the study of turbulent cascade processes
| Project/Area Number |
17K06150
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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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| Research Field |
Fluid engineering
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| Research Institution | Shinshu University |
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Principal Investigator |
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Project Status |
Completed (Fiscal Year 2019)
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| Budget Amount *help |
¥4,810,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥1,110,000)
Fiscal Year 2019: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2018: ¥1,690,000 (Direct Cost: ¥1,300,000、Indirect Cost: ¥390,000)
Fiscal Year 2017: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
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| Keywords | 乱流 / せん断流 / 秩序構造 / カスケード / 二次不安定 / 線形 / アンサンブル平均 / 変曲点不安定 / 渦 / 二次不安定性 / 変曲点 / 境界層 / ストリーク / ヘアピン渦 / カスケート |
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| Outline of Final Research Achievements |
There exist coherent structures such as streaks and hair-pin vortices in the turbulent flow on the wall, and energy is transferred from such a large-scale structure to a small vortex by the cascade process, and these phenomena determine the nature of the turbulent flow. However, it is difficult to grasp the process experimentally because the cascade process caused by various turbulence structures is diverse and irregular in occurrence. In this study, we succeeded in extracting the cascade phenomenon by artificially exciting the periodic disturbance in the turbulent boundary layer and ensemble-averaging the measured flow velocity based on the phase of the excitation. This method of extracting turbulence structure by artificial disturbance excitation and ensemble averaging is considered to be a powerful tool in the research of coherent structures and their cascade processes.
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| Academic Significance and Societal Importance of the Research Achievements |
乱流研究で重要なカギとなる「秩序構造」と「カスケード過程」などの乱流現象については，数値シミュレーションなどでその現象を捉えることができつつあるが，その普遍的な構造や性質については定量的評価が困難であった。今回開発された人工撹乱励起とアンサンブル平均による乱れ構造抽出法は，乱流現象を定量的に評価するだけでなく，現象の時間変化の一般化を可能にしており，乱流を理解する上で重要な発見である。この乱れ構造抽出法は今後の乱流研究において強力かつ主要となるツールとなると予想される。
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Report
(4 results)
Research Products
(20 results)
