| Project/Area Number |
09650533
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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 |
構造工学・地震工学
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| Research Institution | Chuo University |
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Principal Investigator |
HIRANO Hirokazu Chuo University, Faculty of Policy Studies, Professor, 総合政策学部, 教授 (80256023)
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| Co-Investigator(Kenkyū-buntansha) |
KASHIYAMA Kazuo Chuo University, Faculty of Science and Engineering, Professor, 理工学部・土木工学科, 教授 (10194721)
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| Project Period (FY) |
1997 – 1999
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| Project Status |
Completed (Fiscal Year 1999)
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| Budget Amount *help |
¥2,600,000 (Direct Cost: ¥2,600,000)
Fiscal Year 1999: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1998: ¥500,000 (Direct Cost: ¥500,000)
Fiscal Year 1997: ¥1,400,000 (Direct Cost: ¥1,400,000)
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| Keywords | Numerical analysis / Aerodynamic Stability / 3-Dimensional Flow / rectangular Cylinder / separation shear layer / 風洞実験 / 空気力係数 |
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| Research Abstract |
It has become clear that 3-dimensional analysis is required in a certain Reynolds number range, when expressing, by numerical fluid flow analysis, the accurate aerodynamic characteristics and the state of flow around a rectangular sectioned member in which the separation shear layer separates at the front edge and reattaches to the rear surface of the member, as represented by a flat surfaced box-girder bridge. The main results are the following:
(1) The 3-dimensional analysis facilitates qualitative understanding of the aerodynamic characteristics and the state of flow around a rectangular member indicated by the results of wind tunnel tests. Moreover, the separation shear layer which separated at the front edge reattaches in the range between 2.5D and 3.0D. This phenomenon cannot be caught by 2-dimensional analysis.
(2) Except for the front face of the rectangular sectioned member, the average pressure coefficient shows a totally different distribution between the 2-dimensional analysis and 3- dimensional analyses. Large fluctuations are observed in the 2-dimensional analysis, and this is one of the factors in the overestimation or underestimation of aerodynamic forces in 2-dimensional analysis.
(3) In 2-dimensional analysis, the separation shear layer, which separated at the front edge, reattaches in a position much earlier than the point of reattachment indicated by the wind tunnel tests. Moreover, the pressure fluctuations on the surface are greater because of the greater strength of the vortex formed. This is believed to be one of the causes which produce high-frequency components in the fluctuating lift. The reason fluctuating flow in axial direction cannot be expressed by 2-dimensional analysis is the impossibility of correctly evaluating energy dissipation.
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