2019 Fiscal Year Final Research Report
Energy Exchange Mechanism on the Turbulent and non-turbulent Interface by means of Intermediate Mean Kinematic Energy Based on 5-component Decomposition
| Project/Area Number |
17K06160
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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 | Yamaguchi University |
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Principal Investigator |
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| Co-Investigator(Kenkyū-buntansha) |
鈴木 博貴 山口大学, 大学院創成科学研究科, 助教 (10626873)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | 乱流境界層 / エントレインメント / 壁面せん断応力 / エネルギー変換 / エネルギー散逸 |
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| Outline of Final Research Achievements |
The turbulent-nonturbulent interface in the boundary layers has been investigated experimentally. Five-component decomposition of the fluctuating velocities are introduced and equations for momentum and kinematic energy of turbulent and nonturbulent fluids are derived to discuss energy convert mechanisms. The experiment was made in an equilibrium turbulent boundary layer subjected to accelerating free stream velocity. The correction to the logarithmic velocity profile considering non-parallel streamline works well under the favorable pressure gradient. The wake component in the outer layer disappears without entrainment. The diffusion in the turbulent kinematic energy equation is strongly suppressed in the outer layer. The interaction between turbulent and nonturbulent fluids can be examined with the aid of convert terms involved the equation derived from five-component decomposition. Motions contributing energy convert can be detected by investigating the production terms.
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| Free Research Field |
流体工学
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| Academic Significance and Societal Importance of the Research Achievements |
乱流境界層は航空機や自動車，ダクト内に広く存在し，エネルギー効率を左右する．これを理解することは，抵抗や騒音の低減を導き，CO2削減も可能とする．本研究はエネルギー消費の源であるエントレインメントを力学的に調査する方法の開発に焦点を当てた．平衡境界層という最適な条件を設定し，高精度の速度と壁面せん断応力の測定の下で研究した．エントレインメントを引き起こす具体的な乱流運動の検出に成功した．エネルギー消費の源になる運動を特定できた成果は，摩擦抵抗や騒音の低減などの流れの制御技術の開発に役立つものである．
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