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Wind and Structures Volume 9, Number 2, March 2006 , pages 109-124 DOI: https://doi.org/10.12989/was.2006.9.2.109 |
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Characteristics of fluctuating lift forces of a circular cylinder during generation of vortex excitation |
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Sangil Kim and Hiroshi Sakamoto
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| Abstract | ||
| This paper describes the characteristics of the fluctuating lift forces when a circular cylinder vibrates in the cross-flow direction. The response characteristics on elastically supported the circular cylinder was first examined by a free-vibration test. Next, flow-induced vibrations obtained by the free-vibration test were reproduced by a forced-vibration test, and then the characteristics of the fluctuating lift forces, the work done by the fluctuating lift, the behavior of the rolling-up of the separated shear layers were investigated on the basis of the visualized flow patterns. The main findings were that (i) the fluctuating lift forces become considerably large than those of a stationary circular cylinder, (ii) negative pressure generates on the surface of the circular cylinder when the rolling-up of separated shear layer begins, (iii) the phase between the fluctuating lift force and the cylinder displacement changes abruptly as the reduced velocity Ur increases, and (iv) whether the generating cross-flow vibration becomes divergent or convergent can be described based on the work done by the fluctuating lift force. Furthermore, it was found that the generation of cross-flow vibration can be perfectly suppressed when the small tripping rods are installed on the surface of the circular cylinder. | ||
| Key Words | ||
| circular cylinder; cross-flow vibration; vortex excitation; fluctuating fluid forces; displacement; separated shear layers; phase. | ||
| Address | ||
| Department of Mechanical Engineering, KitamiInstitute of Technology, 165 Koen-cho, Kitami, Hokkaido 090-8507, Japan | ||