Tension and Drag Forces of Flexible Risers Undergoing Vortex-Induced Vibration |
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| Authors: | SONG Lei-jian FU Shi-xiao LI Man GAO Yun and MA Lei-xin |
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| Institution: | State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai 200240, China,State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200240, China;Collaborative Innovation Center for Advanced Ship and Deep-Sea Exploration, Shanghai 200240, China,Marine Design & Research Institute of China, Shanghai 200011, China,State Key Laboratory of Oil and Gas Reservoir Geology and Exploration, Southwest Petroleum University, Chengdu 610500, China and State Key Laboratory of Ocean Engineering, Shanghai Jiao Tong University, Shanghai 200240, China |
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| Abstract: | This paper presents the results of an experimental investigation on the variation in the tension and the distribution of drag force coefficients along flexible risers under vortex-induced vibration (VIV) in a uniform flow for Reynolds numbers (Re) up to 2.2×105. The results show that the mean tension is proportional to the square of the incoming current speed, and the tension coefficient of a flexible riser undergoing VIV can be up to 12. The mean drag force is uniformly and symmetrically distributed along the axes of the risers undergoing VIV. The corresponding drag coefficient can vary between 1.6 and 2.4 but is not a constant value of 1.2, as it is for a fixed cylinder in the absence of VIV. These experimental results are used to develop a new empirical prediction model to estimate the drag force coefficient for flexible risers undergoing VIV for Reynolds number on the order of 105, which accounts for the effects of the incoming current speed, the VIV dominant modal number and the frequency. |
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| Keywords: | flexible riser drag force tension force vortex-induced vibration |
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