2001 Fiscal Year Final Research Report Summary
Study on Flow-Induced In-Line Oscillation of a Structure in the Pipe System of Industrial Plants in the Region of High Reynolds Number
| Project/Area Number |
11450074
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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 | Kanazawa University |
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Principal Investigator |
OKAJIMA Atsushi Kanazawa University, Faculty of Engineering, Professor, 工学部, 教授 (80013689)
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| Co-Investigator(Kenkyū-buntansha) |
UENO Hisanori Kanazawa University, Faculty of Engineering, Professor, 工学部, 教授 (80019752)
MIZOTA Takehito Fukuoka Institute of Technology, Faculty of Engineering, Professor, 工学部, 教授 (10038557)
OKANO Yukimitsui Institute of Nuclear Safety System, Incorporated, Depute Director General, 技術システム研究所, 副所長
KIWATA Takahiro Kanazawa University, Faculty of Engineering, Associate Professor, 工学部, 助教授 (40225107)
KIMURA Sigeo Kanazawa University, Faculty of Engineering, Professor, 工学部, 教授 (70272953)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Flow-induced vibration / In-Line Oscillation / Bluff body / High Reynolds number / Reducedmass damping parameter / Circular cylinder / Aspect ratio / Taperd circular cylinder |
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| Research Abstract |
Flow-induced vibration of bluff bodies occurs in industrial plants such as nuclear power plants, petroleum/chemical plants and offshore platforms. Usually, a thermocouple and a sensor probe are inserted in the pipe system. If the working fluid is a liquid, such cantilever-shaped structures with extremely small mass ratios may be easily induced by the flow to oscillate. For example, the damage to a thermocouple in the fast breeder reactor "Monju" of the Japan Nuclear Cycle Development Institute in 1995 was caused mainly by a stream wise flow-induced vibration. Vortex shedding from an elastically supported cylinder can cause the cylinder to oscillate in the transverse (cross-flow) and strea mwise (in-line) directions if the damping of the system is small.
Flow-induced in-line oscillation of a circular cylinder was studied by free-oscillation tests in a water tunnel and a wind tunnel and also by numerical simulations. In a water tunnel and a wind tunnel, we carried out multiple experimenta
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l studies where a circular cylinder was elastically supported at both ends and where the cylinder was cantilevered. The structure damping parameter was varied over a wide testing range to evaluate the critical value at which the in-line oscillation response is suppressed, when a cylinder is supported at both ends and cantilevered. Response amplitudes of a circular cylinder have been measured and computed for evaluating the values of the reduced mass-damping parameter of less than 1.0. In the free-oscillation tests, the cylinder models were spring-mounted so as to oscillate as a two-dimensional rigid cylinder in the water and wind tunnels. Two types of excitation phenomena appear at approximately half of the resonance flow velocity. The response amplitudes are sensitive to the reduced mass-damping parameter during the in-line oscillation of the first excitation region with a symmetric vortex street, and the alternate vortices are periodically shed, locking-in with the vibration of the cylinder in the second excitation region. A hysteresis phenomenon is observed to appear in the in-line oscillation of the latter region. A cantilevered circular cylinder with a finite length aspect ratio of 10 was tested for fluid-elastic characteristics of the cylinder, and these characteristics are found to be quite different from those of the two-dimensional cylinder, having only one wide velocity region of excitation. The results measured by experiments in the water tunnel and the wind tunnel, and predicted by numerical simulations are in fair agreement. The results of this study are providing important supporting data for the recent publication "Guideline for Evaluation of Flow-Induced Vibration of a Cylindrical Structure in a Pipe" by the Japan Society of Mechanical Engineers, Standard JSME S012-1998. Less
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