Abstract An innovative concept for a Spar-type floating wind turbine incorporating aquaculture cages was proposed before. This concept not only meets the Sustainable Development Goals but also optimizes the use of offshore ocean space. The integration of floating offshore wind turbines with aquaculture has the potential to bring economic benefits to both industries. In the present study, a 1/56 scale model of a 2MW Spar floating wind turbine is used and the target cage is a silver salmon farming cage with dimensions of around 25 m in diameter and 9 m in depth in practice. An experimental and numerical investigation was carried out in an ocean engineering basin to examine the motion responses of a Spar-type floating offshore wind turbine and aquaculture cage with different configurations against the wave direction, respectively. The surge, heave, and pitch response amplitude operators of the Spar-type floating structure and the non-dimensionalized horizontal and vertical displacement of the aquaculture net cage were examined under regular wave conditions with periods from 0.6 s to 1.4 s. The aquaculture net cage was positioned in front of and behind the Spar-type floating structure facing the wave direction. Accelerometers recorded the motion responses of both the Spar-type floating structure and the net cage. Based on the experimental results, the presence of an aquaculture net cage has a significant effect on the motion responses of the Spar-type floating structure. First, because of the shadowing effect, the presence of the net cage generally reduces the 20% surge motion responses of the Spar, especially when the net cage is set at the back of the Spar relative to the wave direction. However, the presence of the net cage has a small effect on the heave motion responses while the heave motion shows a tendency to decrease. In addition, the presence of the net cage enhances the pitch motion responses of the Spar when the wave period is greater than 1.0 s, and this scenario is especially pronounced when the net cage is located behind the Spar. On the other hand, the non-dimensionalized horizontal displacement of the net cage tends to increase with the increasing distance to the Spar under short wave period conditions but decreases under long wave period conditions regardless of their distance. The vertical non-dimensional displacement of the cage increases under short wave period conditions and changes insignificantly under long wave period conditions. Also, a numerical simulation performed by OrcaFlex shows that compared with the experimental results the vertical motion responses of the Spar and net cage agree well. However, for other motion responses of the Spar and net cage, the numerical results differ significantly from the experimental results.
Bai et al. (Sun,) studied this question.