Vortex-Induced Vibrations of Two Flexible Cylinders in Tandem Arrangement With Discrete Vortex Method
- Ke Lin (Shanghai Jiao Tong University) | Jiasong Wang (Shanghai Jiao Tong University) | Jianliang Zhou (CNOOC Research Center) | Liangbin Xu (CNOOC Research Center) | Leixiang Sheng (CNOOC Research Center)
- Document ID
- International Society of Offshore and Polar Engineers
- The 28th International Ocean and Polar Engineering Conference, 10-15 June, Sapporo, Japan
- Publication Date
- Document Type
- Conference Paper
- 2018. International Society of Offshore and Polar Engineers
- flexible risers, VIV, DVM, tandem arrangement
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We present numerical simulation on the vortex-induced vibrations (VIV) of two flexible cylinders, placed within a stepped oncoming flow in a tandem arrangement with near wake interference, using a discrete vortex method (DVM). The numerical model of cylinders are referred to the experimental configuration of Huarte and Bearman (2011), with aspect ratio of 93.75. The simulations are conducted at the Reynolds numbers from 4800 to 12000. Both two cylinder are free to oscillate in the in-line and cross-flow directions. Based on the strip theory, the three-dimensional flow field around the flexible cylinders is approximately simulated, with the two-dimensional vorticity transport equation numerically solved by the discrete vortex method in Lagrangian grid-independent frame. The dynamic equation of two cylinders are solved by the finite element method. Compared with the experimental results, the present simulation well predicts the VIV response mode, amplitudes and frequencies of two cylinders-Numerical results reveal the differences in dynamic responses of the upstream and downstream cylinders compared with that of VIV of isolated cylinder, which is expected to be associated with the occurrence of wake interference. Visualized by the distribution of vortex elements, the wake patterns are presented to investigate the vortex motion associated with the wake interference.
Vortex-induced vibration (VIV) is the motions induced by periodically shedding of the asymmetric vortices when fluid flows around the body of bluff section. In practical engineering applications, there are many VIV problems that involve the structure in configuration of two or more cylinders, such as the TLP platform, submarine pipelines, large floating body and overhead conductor cables, etc. The cylinders in multiple configuration are not only subjected to the VIV but also the wake-induced vibrations (WIV) that are associated with the wake interference. The interaction of vortex and wake-induced vibrations trends to cause the significant and complex dynamic response of the structure, which increases the risk of fatigue and collusion damage of the multiple cylindrical structures, especially in the multi-riser system of offshore drilling platform.
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