2003 Fiscal Year Final Research Report Summary
Flip-Flop Flow Mechanism in Diamond-Shaped Cylinder Bundles
| Project/Area Number |
14550166
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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 | FUKUYAMA University |
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Principal Investigator |
SHINZABURO Umeda FUKUYAMA University, Department of Civil and Environmental Engineering, Professor, 工学部, 教授 (90031145)
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| Co-Investigator(Kenkyū-buntansha) |
WEN?JEI Yang アメリカ・ミシガン大学, 工学部, 教授
YANG Wen-jei University of Michigan, Department of Mechanical Engineering, Emeritus Professor
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| Project Period (FY) |
2002 – 2003
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| Keywords | Flip-flop flow / Diamond-shaned cylinder bundle / Intersecting flow / LDV / PIV / Edge-tone |
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| Research Abstract |
A self-induced flip-flop flow phenomenon in diamond-shaped cylinder bundles has been disclosed, in previous studies by the authors. The flip-flop flow oscillation promotes fluid mixing and thus contributes to an enhancement in convective heat and mass transfer when the cylinder bundles are used as heat and mass exchanger equipment. In the present study, both two-dimensional particle image velocimetry(PIV) and two-dimensional laser Doppler velocimetry(LDV) were performed to observe and monitor flow phenomena in diamond-shaped cylinder bundles for the purpose of investigating flip-flop flow mechanisms. The following summary is derived from this study:
The mechanisms for the occurrence of flip-flop flow oscillation in the flow channels of a diamond-shaped cylinder bundle are summarized in the form of a flow chart. It consists of necessary and auxiliary conditions. The necessary conditions include the generation of separation vortices, fluctuations of von Karman vortex sheets, occurrence of Coanda effect, and variation of flow cross-sectional areas. Intersecting flows, ramming effect, energy source point and shear layer oscillation are considered the auxiliary conditions. A minimum of three rows in a cylinder bundle warrants the occurrence of edge-tone phenomenon(generation of pressure wayes) at the leading edge of the fourth-row cylinder and the reciprocating migration of a conjunct separation vortex pair across the rear apex of the third-row cylinder. The latter triggers the fluctuation of flip-flop flow downstream in a diamond-shaped cylinder bundle of more than five rows and a stable swinging of exit jets from the bundle.
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