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Liu, Mingyue,Xiao, Longfei,Lu, Haining,Xiao, Xiaolong The Society of Naval Architects of Korea 2017 International Journal of Naval Architecture and Oc Vol.9 No.3
The Vortex-induced Motions (VIM) phenomenon of semi-submersibles is relevant for the fatigue life of moorings and risers. Model tests regarding the VIM behavior of a semi-submersible with four square columns were conducted in order to investigate the effects of the current incidence and the aspect ratio of the immerged column. The experimental results show that the largest transverse amplitudes are around 70% of the column width at $30^{\circ}$ and $45^{\circ}$ incidences in a range of reduced velocities from 5 to 8 when the aspect ratio of the immerged column is 1.90. The largest yaw motion occurs at $0^{\circ}$ incidence with the peak value around $4.5^{\circ}$. Similar characteristics of the VIM response are observed for the semi-submersible with aspect ratios of 1.90 and 1.73. When the aspect ratio decreases 50% to 0.87, 30% decrease in the peak transverse amplitudes can be seen.
Mingyue Liu,Longfei Xiao,Haining Lu,Xiaolong Xiao 대한조선학회 2017 International Journal of Naval Architecture and Oc Vol.9 No.3
The Vortex-induced Motions (VIM) phenomenon of semi-submersibles is relevant for the fatigue life of moorings and risers. Model tests regarding the VIM behavior of a semi-submersible with four square columns were conducted in order to investigate the effects of the current incidence and the aspect ratio of the immerged column. The experimental results show that the largest transverse amplitudes are around 70% of the column width at 30 and 45 incidences in a range of reduced velocities from 5 to 8 when the aspect ratio of the immerged column is 1.90. The largest yaw motion occurs at 0 incidence with the peak value around 4.5. Similar characteristics of the VIM response are observed for the semi-submersible with aspect ratios of 1.90 and 1.73. When the aspect ratio decreases 50% to 0.87, 30% decrease in the peak transverse amplitudes can be seen.
Numerical studies on flow-induced motions of a semi-submersible with three circular columns
Tian Chenling,Liu Mingyue,Xiao Longfei,Lu Haining,Wang Jin 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1
The semi-submersible with three circular columns is an original concept of efficient multifunctional platform, which can be used for marginal oil, gas field, and Floater of Wind Turbines (FOWT). However, under certain flow conditions, especially in uniform current with specific velocities, the eddies will alternatively form and drop behind columns, resulting in the fluctuating lift force and drag force. Consequently, the semi-submersible will subject to the Flow-Induced Motions (FIM). Based on the Detached Eddy Simulation (DES) method, the numerical studies were carried out to understand the FIM characteristics of the three-column semi-submersible at two different parameters, i.e., current incidences (0, 30, and 60-incidences) and reduced velocities (4 Ur 14). The results indicate that the lock-in range of 6 Ur 10 for the transverse motions is presented, and the largest transverse nondimensional nominal amplitude is observed at 60-incidence, with a value of Ay=D ¼ 0:481. The largest yaw amplitude Ayaw is around 3.0 at 0-incidence in the range of 8 Ur 12. The motion magnitude is basically the same as that of a four-column semi-submersible. However, smaller responses are presented compared to those of the three-column systems revealing the mitigation effect of the pontoon on FIM.