2005 Fiscal Year Final Research Report Summary
Study on Frictional Resistance of Drag Reducing Solid Wall
| Project/Area Number |
15360099
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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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| Research Field |
Fluid engineering
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| Research Institution | Tokyo Metropolitan University |
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Principal Investigator |
MIZUNUMA Hiroshi Tokyo Metropolitan University, Assistant Professor, 都市教養学部, 助教授 (20117724)
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| Co-Investigator(Kenkyū-buntansha) |
MORONUKI Nobuyuki Tokyo Metropolitan University, Professor, システムデザイン学部, 教授 (90166463)
YANG Ming Tokyo Metropolitan University, Assistant Professor, システムデザイン学部, 准教授 (90240142)
OGATA Satoshi Tokyo Metropolitan University, Research Associate, 都市教養学部, 研究員 (50315751)
WATANABE Keizo Tokyo University of Agriculture and Technology, Professor, 工学部, 客員教授 (20072134)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Fluid mechanics / Newtonina fluid / Drag reduction / Flow in a Duct / Flow past a sphere / Hydrophobic Surface / Disk with Fine Grooves / Shear-Force Pump |
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| Research Abstract |
In this study, we studied on the flow characteristics of a tap water or glycerin solutions for the flow in a duct, the flow past a sphere, and the flow in an enclosed rotating disk with a drag reducing surface.
For a flow in a duct with hydrophobic coating surface, it was clarified that the laminar drag reduction occurred in the Reynolds number range of 150 <Re < 770. The maximum drag reduction ratio is 12.6% at Re = 649.
For the flow past a sphere, it was clarified that the vortex street was not found at the Re < 320 in the hydrophobic wall and the separation point moved downstream compared with that of a conventional smooth wall. The drag reduction occurred in the flow and the maximum drag reduction ratio was 14.6% at the Re=93.2. In this simulation, the method for tracking gas-liquid interfaces has been used the VOF technique, and the method for modeling surface tension effects on fluid motion has been used the CSF model. The flow patterns for the numerical simulation results agreed with that of the flow visualization results.
For the flows around an enclosed rotating disk with the fine spiral grooves, it was seen that the drag reduction occurs in the turbulent flow range at the non-dimensional axial clearance (s/a) = 0.011, 0.22 and 0.33, the maximum drag reduction ratio is approximately 15%. The fine spiral groove has the effect which suppresses the development of the fluctuation of transition region, and which delays the generation of the local turbulence in the transition range.
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