| Abstrakt: |
With the development of offshore oil production and the resulting application of riser pipes, it is necessary to get a better understanding of the flow-induced vibrations (FIV) phenomenon involving multiple cylindrical structures. In this scenario, little is available concerning the phase difference between the transverse displacements of two long rigid cylinders (aspect ratio of 30) in tandem and free to vibrate due to the flow incidence. Aiming to fill this gap, experiments were carried out at the towing tank of the Technological Research Institute (IPT) for two similar rigid cylinders in a tandem arrangement. Both cylinders were elastically supported with two degrees of freedom (2DOF), the in-line and transverse direction. Different tandem distances were tested ( T = 2 D , 2.5D, 3D, 4D and 6D) throughout the complete excitation of the lock-in range for the upstream cylinder, i.e., reduced velocities ranged from 3 to 13, which corresponds to Reynolds numbers from 3 × 10 3 to 3 × 10 4 . This work found the upstream cylinder having a qualitatively similar response compared with the isolated one. The downstream cylinder exhibited large response amplitudes compared with the upstream one in the lower branch of vibration. Lastly, the phase difference between transverse displacements of both cylinders was classified according to five phase patterns, two of them apparently related to the initial and upper branches of vibration in all cases. [ABSTRACT FROM AUTHOR] |
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