Hydrodynamic model testing of a semi-submersible wind-tidal current combined power generation platform

With the advancement of ocean energy development and utilization technology, the integration of multiple energy sources in combined power generation devices has emerged as a prominent trend in ocean energy equipment research. In this paper, a Semi-submersible Wind-Tidal current (SWT) combined power generation platform is designed based on the ''WindFloat'' semi-submersible platform and NREL 5 MW wind turbine. An adaptive mooring system is also developed for SWT. A physical model test, conducted at a scale ratio of 1:50 in an ocean engineering basin, is utilized to evaluate the hydrodynamic performance of the SWT under various conditions. The test included the free decay test, RAO (Response Amplitude Operator) test under the regular wave, irregular wave response, and wind-wave combined action tests. The experimental results provide comprehensive data, verifying the operational feasibility of SWT platform. At the same time, the impact of different environmental factors (wind, wave) on the motion response of the SWT is analyzed in this paper. The test result shows that the wind load increases SWT surge direction RAO value, but decreases RAO values in other degrees of freedom during regular wave tests. Irregular wave tests reveal that heave motion response is most affected by test conditions, while sway motion experiences minimal impact, and pitch motion exhibits greater intensity. Additionally, analysis of power spectrum curves from coupled wind-irregular wave tests demonstrates phenomena such as “dual-peak” and peak shift, with evident amplification due to wind effects on power spectrum peaks. The experimental process and research findings presented herein can serve as valuable references for future offshore multi-energy complementary utilization devices' model testing and numerical simulation studies.