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Wind and Structures Volume 26, Number 2, February 2018 , pages 57-68 DOI: https://doi.org/10.12989/was.2018.26.2.057 |
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Experimental study on wake-induced vibrations of two circular cylinders with two degrees of freedom |
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Xiaoqing Du, Benjian Jiang, Chin Dai, Guoyan Wang and Suren Chen
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| Abstract | ||
| Wind tunnel tests are conducted to investigate wake-induced vibrations of two circular cylinders with a center-to-center spacing of 4 diameters and attack angle varying from 0 to 20 for Reynolds numbers between 18,000 and 168,800. Effects of structural damping, Reynolds number, attack angle and reduced velocity on dynamic responses are examined. Results show that wake-induced vortex vibrations of the downstream cylinder occur in a wider range of the reduced velocity and have higher amplitudes in comparison to the vortex-induced vibration of a single circular cylinder. Two types of wake-induced instability phenomena with distinct dynamic characteristics are observed, which may be due to different generation mechanisms. For small attack angles like 5 and 10, the instability of the downstream cylinder characterizes a one-degree-of-freedom (1-DOF) oscillation moving in the across-wind direction. For a large attack angle like 20, the instability characterizes a two-degree-of-freedom (2-DOF) oscillation with elliptical trajectories. For an attack angle of 15, the instability can transform from the 1-DOF pattern to the 2-DOF one with the increase of the Reynolds number. Furthermore, the two instabilities show different sensitivity to the structural damping. The 1-DOF instability can be either completely suppressed or reduced to an unsteady oscillation, while the 2-DOF one is relatively less sensitive to the damping level. Reynolds number has important effects on the wake-induced instabilities. | ||
| Key Words | ||
| two circular cylinders; wind tunnel test; wake-induced vibration; Reynolds number effect | ||
| Address | ||
| Xiaoqing Du and Benjian Jiang: Department of Civil Engineering, Shanghai University, Shanghai, China Chin Dai: Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai, China Guoyan Wang: School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, China Suren Chen: Department of Civil and Environmental Engineering, Colorado State University, Colorado, United States | ||