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An experimental investigation on interfering VIVs of double and triple unequal-diameter flexible cylinders in tandem
Marine Structures ( IF 3.9 ) Pub Date : 2022-05-19 , DOI: 10.1016/j.marstruc.2022.103247
Bing Zhao, Shixiao Fu, Mengmeng Zhang, Haojie Ren, Liangbin Xu, Wenhui Xie, Lusheng Jia

Many unequal-diameter risers have been widely applied to satisfy different operational requirements in ocean oil and gas drilling engineering, and adjacent tandem risers can undergo complex vibration responses and even collisions under ocean flow conditions. To investigate the wake interference responses for multiple risers in tandem configuration, an experiment of double and triple unequal-diameter flexible cylinders was conducted under uniform flow with Reynolds numbers Re ranging from 2832 to 11,328 for the larger cylinder and from 1805 to 7220 for the smaller cylinder. The two cylinders were 8 m in length with aspect ratios equal to 282.49 and 443.21, respectively, and the corresponding diameter ratio was 0.64. Two different tandem configurations were arranged with a large cylinder upstream and downstream, and the wall spacing between adjacent cylinders was fixed at 4D, where D is the diameter of small cylinders. Fiber Bragg grating strain sensors were used to measure both in-line (IL) and cross-flow (CF) strain responses. The modal superposition method was applied to reconstruct displacement responses based on measured strains, and drag forces were further inversely identified from the mean IL displacements. Equivalent wake velocities were calculated from drag force reductions. The results show that the downstream large cylinder in a triple-cylinder system endures a stronger wake interference effect than that in a double-cylinder system. Wake interference can decrease the dominant mode of downstream cylinders and increase the vibration amplitudes due to the reduction in the local wake velocity. In addition, a downstream cylinder undergoing wake-induced vibrations has the same dominant frequency in the CF and IL directions, and its CF frequency is identical to that of the upstream cylinder.



中文翻译:

串联双、三不等径柔性圆柱体干扰VIV的实验研究

许多不等径立管已被广泛应用,以满足海洋油气钻井工程中不同的作业要求,而相邻的串联立管在洋流条件下会经历复杂的振动响应甚至碰撞。为了研究串联配置的多个立管的尾流干扰响应,在雷诺数Re的均匀流动下进行了双和三不等直径柔性圆柱体的实验。较大气缸的范围从 2832 到 11,328,较小气缸的范围从 1805 到 7220。两个圆柱体长 8 m,纵横比分别为 282.49 和 443.21,对应的直径比为 0.64。两种不同的串联配置,上游和下游都有一个大圆柱体,相邻圆柱体之间的壁间距固定为 4 D,其中D是小圆柱的直径。光纤布拉格光栅应变传感器用于测量在线 (IL) 和横流 (CF) 应变响应。应用模态叠加方法基于测量的应变重建位移响应,并从平均 IL 位移进一步反向识别阻力。等效尾流速度是根据阻力减少计算的。结果表明,与双缸系统相比,三缸系统下游大缸的尾流干扰效应更强。由于局部尾流速度的降低,尾流干扰可以减少下游气缸的主要模式并增加振动幅度。此外,

更新日期:2022-05-19
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