Vortex-induced vibration and mode transition of a curved flexible free-hanging cylinder in exponential shear flows |
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Institution: | 1. College of Engineering, Ocean University of China, Qingdao, 266100, China;2. College of Architecture and Civil Engineering, Shandong University of Science and Technology, Qingdao, 266590, China |
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Abstract: | This paper presents an experimental study of vortex-induced-vibration (VIV) of a curved flexible free-hanging cylinder in exponential shear flows. The emphasis is on previously unexplained phenomena in our early research and in some cases offers insights on the mode transition of nonlinear vibration behavior of long flexible cylinders. The experimental results illustrate that the cylinder undergoes multi-frequency response and the dominant frequency varies spatially. The IL and CF response and transition are out-of-sync. In the second (2nd) mode response, the spanwise response exhibits a mixed pattern with standing wave and traveling wave. The contribution of traveling wave becomes greater as the reduced velocity increases. Only two distinct branches of response, namely the initial and lower branches, are observed in each mode. The lower branches of the first (1st) and 2nd modes present the same normalized frequency. A phase jump around 180°occurs at the transition between initial branches and lower branches, accompanying with a switch between 2S 2P or P+S vortex shedding modes. |
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Keywords: | Vortex induced vibration Flexible cylinder Shear flow Mode transition |
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