| Project/Area Number |
03452141
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
機械力学・制御工学
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| Research Institution | Science University of Tokyo |
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Principal Investigator |
HARA Fumio Science University of Tokyo, Department of Mechanical Engineering, Professor, 工学部第一部, 教授 (90084376)
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| Project Period (FY) |
1991 – 1992
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| Project Status |
Completed (Fiscal Year 1992)
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| Budget Amount *help |
¥6,200,000 (Direct Cost: ¥6,200,000)
Fiscal Year 1992: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1991: ¥4,300,000 (Direct Cost: ¥4,300,000)
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| Keywords | Rotating cylinder-shaft system / Self-excited Vibration / Flow-induced vibration / Unsteady fluid force / Work done / Swirling wave / Phase-lead force / 半浸水回転円筒・軸系の振動 / 励振メカニズム / 振動エネルギ的検討 / 不安定振動 |
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| Research Abstract |
It is well known in vibration field that the rotating cylinder-shaft system undergoes a violent vibration when it is operated at a high speed of rotation over the critical speed. The unstable vibration occurs under a very limited conditions imposed to the rotation speed, submerging water depth, and the natural frequency of the cylinder-shaft system.
1) The experimental apparatus was constructed to measure the unsteady fluid force acting on the rotating cylinder when it was forced to oscillate sinusoidally with a constant amplitude. We measured the unsteady fluid force and the displacement of the rotating cylinder simultaneously and evaluated the energy per unit time produced by the unsteady fluid force on the cylinder system. The energy was evaluated for the combinations of experimental parameters; rotation speed, oscillation frequency, amplitude, and submerging water depth.
2) We found the unsteady fluid force was of phase-angle lead to the cylinder displacement which resulted in the energy positive for a very limited range of rotation speed and oscillation frequency.
3) The cylinder-shaft system underwent an unstable vibration when it was operated under the same condition specified by the above.
4) We took video picture of the rotating cylinder and swirling wave generated around the cylinder when it undertook the unstable vibration and analysed the time series video images. It was found the wave generated around the rotating cylinder has the same frequency as the natural one of the cylinder-shaft system when the unstable vibration occurred.
5) The research concludes that the flow-induced unstable vibration occurred in the rotating cylinder-shaft system is strongly associated with the fluid wave generated around the cylinder. However the theoretical investigation is still needed to clarify the mechanism governing the unstable vibration which must be based on the experimental results shown in this report.
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