Comparision of Integrated Towing Motion Performance for Multi-Column Semisubmersible Floating Offshore Wind Turbines

Abstract

[Introduction] A comparative research was conducted to investigate the variation rules of motion responses in various degrees of freedom (DOF) and towline forces in the towing process of three-column submerged floating offshore wind turbines (TC-SFOWT) and four-column submerged floating offshore wind turbines (FC-SFOWT) under different working conditions, through a physical model test using a DTU 10 MW wind turbine. [Method] Firstly, a free attenuation test was carried out in still water. Then towing process tests were carried out in regular wave and irregular wave environments. The research focuses on the effects of different towline point heights, wave heights, and wave periods on the towing process of SFOWTs. [Result] These tests yielded the following findings. (1) The analysis related to heave, roll, and pitch natural vibration periods of SFOWTs reveals that the difference in natural vibration periods between the two SFOWT structures in the same DOF is within 5 seconds, the TC-SFOWT exhibits a smaller heave acceleration and longer natural periods of pitch and roll; (2) As wave height increases, the response of SFOWTs in each DOF and the towline force also increase, and the increase in wave height has a greater influence on the heave acceleration and roll angle of the TC-SFOWT under both regular wave and irregular wave conditions, while it has a smaller impact on the pitch angle and towline force; (3) When the wave period differs greatly from the natural period of SFOWTs, an increase in wave period results in a decreasing trend in the SFOWTs' responses across various DOFs, except for heave acceleration; (4) When the towline point is flush with the water level, the towline force amplitudes of the TC-SFOWT and FC-SFOWT are respectively 11.1% and 14.7% lower than those of the other two working conditions. [Conclusion] In conclusion, the towing motion performance of the FC-SFOWT is better. In actual engineering practices, the towline point height when the structure is self-floating should be arranged at the water surface line, so as to reduce motion response during the towing process.

Keywords

• dtu 10 mw
• submerged floating offshore wind turbine
• integrated towing
• motion response
• free attenuation
• model test