| Project/Area Number |
15560412
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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 |
Structural engineering/Earthquake engineering/Maintenance management engineering
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| Research Institution | Ritsumeikan University |
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Principal Investigator |
KOBAYASHI Hiroshi Ritsumeikan University, Faculty of Science and Engineering, Professor, 理工学部, 教授 (90066712)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥2,500,000 (Direct Cost: ¥2,500,000)
Fiscal Year 2004: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 2003: ¥1,500,000 (Direct Cost: ¥1,500,000)
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| Keywords | Rectangular cylinder / Vortex oscillation / Control / Rotor / Pressure / Flow visualization / 過励振 / 風による振動 |
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| Research Abstract |
A rectangular cylinder with width to depth ratio of 4 by 1 causes wind induced oscillation at a specific wind speed region, named vortex oscillation. This oscillation is caused by motion induced vortex which separate from the leading edge of a cylinder synchronizing with the motion of the cylinder.
Rotors with 3 blades are installed at the leading edges of the rectangular cylinder in a wind. These rotors can rotate by the action of wind and require no driving force. The vortex oscillation seen in the cylinder without rotor was suppressed by the rotors. The relation between the control effect and the rotor speed was obtained.
Pressure measurement test with harmonically shaking cylinder was conducted. The result showed that the amplitude of unsteady pressure on the surface of the cylinder, which behaved as the exciting force of the cylinder, was reduced substantially by the rotating effect of the rotor.
Flow visualization test was conducted with the oscillating cylinder. The result showed that the motion induced vortex, which was seen in the rectangular cylinder without rotor and was the cause of vortex oscillation, disappeared. The rotation of the rotor gives momentum to the separated flow at the corner of the cylinder and the separated flow is bent toward the side surface of the cylinder. Thus the formation of motion induced vortex is prevented and the vortex oscillation based on the motion induced vortex is suppressed.
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