Experimental study of a semi-submersible floating wind turbine with aquaculture cages under combined wind and irregular waves

Abstract

The coordinated and integrated development of multiple marine industries is conducive to achieving efficient utilization of the ocean. Here, a novel semi-submersible floating wind power platform integrated with aquaculture cages is proposed. Then, model tests of the innovative floating wind-aquaculture platform (FWAP) with scaling ratio of 1/40 are carried out. Four sea conditions (below rated, rated, cut out and 50-year sea states) and three incident angles of combined wind and waves (0 deg, 90 deg and 180 deg) are considered in the tests. Correspondingly, three typical motion responses of the FWAP, the acceleration response of the wind turbine and the representative mooring line tension are analyzed. The experimental results show that one obvious response peak is mainly found in the response amplitude operator (RAO) curves for the in-plane motion of the new FWAP, including surge, sway and yaw. While for out-of-plane motions including heave, roll and pitch, the RAO curves show two distinct response peaks. Notably, as the environmental conditions progress from below rated to rated, cut out, and finally to 50-year extreme sea state, the motion response of the FWAP becomes increasingly pronounced. Furthermore, the acceleration of the wind turbine under rated and cut out conditions is significantly large, which can be attributed to the effect of rotor rotation. While the maximum mooring line tension in the FWAP is observed at the 50-year sea state, the maximum average tension occurs at the rated condition. The response power spectra of the new FWAP reveal the presence of multiple frequency components. Additionally, the nets can act as an excited or damping effect on the motion of the FWAP, the acceleration of the wind turbine and the mooring line system, depending on the variation of the sea conditions or the incident angle. This study can provide reference for the design improvement and engineering application of such new FWAP.