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| Experimental Investigation on Flow Induced Motion of an Equilateral Triangle Prism |
| ZHANG Jun LIAN Ji-jian LIU Fang XU Guo-bin YAN Xiang |
| State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300072 |
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Abstract According to typical experiments of flow induced motion (FIM) of a circular cylinder, a series of FIM experiments for an equilateral triangle prism elastically mounted in water channel are performed with different system stiffness. The responses of the amplitude and frequency of the prism, along with its frequency spectrum features and wake flow mode, are expounded. Besides, the influence of the system stiffness on the FIM and the wake flow mode is discussed. The test results indicate that the FIM of the prism can be divided into three primary regions: the vortex induced vibration (VIV) branch, the transition branch from VIV to galloping and the galloping branch. Significant FIM response of an equilateral triangle prism on springs develops in an infinite range of flow velocities and without a self-limited response. The transition branch is initiated accompanied with a steep increase in amplitude and a precipitous drop in frequency. The frequency presents “lock-in” phenomenon in the VIV upper branch and the galloping branch. The system stiffness changes the wake flow mode of the prism at the same reduced velocity thus affecting the amplitude and frequency responses. The maximum amplitude ratio for the prism reaches 2.11, which is higher than the maximum amplitude ratio 1.90 for a single circular cylinder. Compared with a circular cylinder, an equilateral triangle prism is more beneficial to improving energy extraction from the flow with low velocity.
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Received: 19 August 2015
Published: 15 October 2016
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