2018 Fiscal Year Final Research Report
Investigation of mechanism of pressure drag generation for a wall bounded shear flow by the second invariant of velocity gradient tensor
| Project/Area Number |
16K06096
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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 | Kindai University |
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Principal Investigator |
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| Research Collaborator |
Mochizuki Shinsuke
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| Project Period (FY) |
2016-04-01 – 2019-03-31
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| Keywords | 二次元チャネル流 / 粗面 / 乱流 / せん断流 / 壁面抵抗 / テンソル第二不変量 |
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| Outline of Final Research Achievements |
The mechanism of pressure drag generation was investigated for a channel flow with transverse roughness elements on one wall. The square rod roughness elements is arranged with the roughness pitch ratio of 2, 4 and 8. The friction coefficient increases with the roughness pitch ratio. The increment is due to the pressure drag acting on the roughness. The pressure drag is occurred by the transport of Reynolds shear stress above the cavity between roughness elements. The profiles of the second invariant of the mean velocity gradient tensor have a negative value near the downstream side wall in the cavity, and the absolute value increases with the roughness pitch ratio. The negative value of the invariant contributes to positive pressure on the side wall and the value of the positive pressure depends on the roughness pitch ratio.
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| Free Research Field |
流体工学
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| Academic Significance and Societal Importance of the Research Achievements |
本研究課題における粗さ要素の配置間隔による流れパターンの差が抵抗値へ及ぼす影響，さらにテンソルの第2不変量に基づく抵抗発生要因を解明することで，壁面形状による圧力抵抗の発生要因の差が明らかとなり，壁面抵抗制御に繋げることができる．また，それにより壁面形状による効率のよい流体輸送方法の提案が可能となる．
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