UNSTEADY VERTICAL WIND FORCES APPLIED ON A LARGE ROOF
| Project/Area Number | 08455264 |
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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 |
Building structures/materials
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| Research Institution | Osaka City University |
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Principal Investigator |
TANIIKE Yoshihito Osaka City University, Fac.of Engineering, Prof., 工学部, 教授 (00111980)
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| Co-Investigator(Kenkyū-buntansha) |
NISHIMURA Hiroaki General Building Research Corporation, 室長
OKANAN Hiroo Osaka Prefectural College of Technology, Dept.of Civil Engineering, prof., 建設工学科, 教授 (20111924)
TANIGUCHI Tetsuro Osaka City University, Fac.of Engineering, Research Assoc., 工学部, 助手 (30231418)
KIUCHI Tatsuhiko Osaka City University, Fac.of Engineering, Lecturer, 工学部, 講師 (30112527)
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| Project Period (FY) |
1996 – 1997
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| Project Status |
Completed(Fiscal Year 1997)
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| Budget Amount *help |
¥6,600,000 (Direct Cost : ¥6,600,000)
Fiscal Year 1997 : ¥3,900,000 (Direct Cost : ¥3,900,000)
Fiscal Year 1996 : ¥2,700,000 (Direct Cost : ¥2,700,000)
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| Keywords | POD Analysis / Stagnation Point / Conical Vortex / Switching / Flow Visualization. / 風圧測定実験 |
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| Research Abstract |
Generally the horizontal wind force is mainly considered for the design of structures. However, in the case that the structure is located at a hilly country or has a large-span roof, the instantaneous vertical wind force must be considered. This vertical wind force is considered to be induced by vortices generated on a roof. The present study is aimed to make clear the mechanism of these vortices by means of the flow visualizations and the wind tunnel experiments concerned with the pressure applied on the roof and the wall of the model.
The flow visualizations with the cubic and the square roof models were carried out when the incident flow is for oblique angle, using the mist vaporized of the alcohol solution. The flow patterns on the roof was observed with laser sheets and a strobe light. On the roof of the square roof model, a pair of conical vortices is observed which are steady similar to those generated on the delta wing. On the other hand, on the roof of the cubic model only one
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conical vortex exists and this changed the side almost alternately. In the following this phenomenon is called the switching.
In order to investigate the cause why switching is induced, the wind tunnel experiments were carried out, which pressures applied on 96 points on the roof and the wall of the model were measured. The obtained time series of pressures were analyzed by Proper Orthogonal Decomposition (POD). POD is the available technique to find the systematic structure from many time records of the pressure which fluctuates randomly. As a result of the case of the model with flat horizontal roof, the most distinguished mode was as follows. The pressures on one side of the roof fluctuate in the opposite direction to of the other side. On the other hand, the pressures on one side wall fluctuate in the opposite direction to the pressures of same side of the roof and the other side wall. These results of the flow visualization and POD analysis means that the conical vortex generated on the opposite side to the wall which the stagnation point exists on. Consequently it is clarified that the switching of conical vortex on the roof is closely related with the position of the stagnation point on the wall. Less
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Report
(3results)
Research Products
(15results)
