2022 Fiscal Year Final Research Report
Study on reduction of airfoil friction-drag and noise by control of turbulent structures in transitional and turbulent regions
| Project/Area Number |
19H02350
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Review Section |
Basic Section 24010:Aerospace engineering-related
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| Research Institution | Tokyo Metropolitan University |
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Principal Investigator |
Asai Masahito 東京都立大学, システムデザイン研究科, 客員教授 (00117988)
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| Co-Investigator(Kenkyū-buntansha) |
稲澤 歩 東京都立大学, システムデザイン研究科, 准教授 (70404936)
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| Project Period (FY) |
2019-04-01 – 2023-03-31
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| Keywords | 流体工学 / 航空宇宙工学 / 乱流 / 乱流遷移 / 境界層 / 空力音 / 抵抗低減 / リブレット |
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| Outline of Final Research Achievements |
Effects of riblets on transitional and turbulent flows and feedback-loop mechanism generating tonal noise were examined. The former focused on yaw-angle effects on the drag reduction rate in turbulent flow. Experiments showed that the drag reducing ability was more sensitive to the yaw angle for trapezoidal riblets than for saw-tooth riblets and was lost when the yaw angle exceeded 15 deg. Impact of riblets on lateral turbulent contamination in laminar boundary layer was also examined. The latter focused on acoustic feedback-loop established when a 2D protuberance existed in laminar boundary layer. Onset of tonal noise required rapid disturbance growth due to strong instability in a small separation bubble formed just upstream of the protuberance. When an additional thin roughness element existed upstream region, the threshold protuberance height decreased below 60% of the value in the absence of roughness element. The adverse pressure gradient also reduced the threshold height.
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| Free Research Field |
流体力学
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| Academic Significance and Societal Importance of the Research Achievements |
実機適用が検討されている台形溝リブレットに対する抵抗低減効果のヨー角依存性に関する研究成果は，乱流制御の基礎資料としてだけでなく，リブレットの実利用におけるロバスト性の検討資料としても意義あるものである．また，遷移域でのリブレットの適用において乱流コンタミネーションへの影響がほとんどないことも特筆すべきことである．層流境界層中の二次元孤立祖度または壁面段差によるフィードバック音発生の臨界条件は空力音抑制を考える上で考慮すべき結果であるとともに，音響フィードバックに関する研究成果は翼の後縁からのトーナルノイズの発生機構や素過程を理解する上でも大いに役立つ．
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