# Numerical Study on Hydrodynamic Performance of a New Semi-Submersible Aquaculture Platform
## 5 Conclusions  
In this paper, a numerical study of the hydrodynamic performance of a newly designed semi-submersible aquaculture platform, developed by GIEC and put into operation, is conducted. The present study proposes a numerical model that considers the semi-submersible main structure, the net system, and the mooring system to accurately capture the dynamic response of the platform under wave, wind, and current conditions. The wave force is calculated based on the linear potential theory and the boundary element method. The wind force and current force are calculated according to the rules of CCS. The net system is modeled based on the Morison equation and the equivalent simulation. The mooring system is modeled based on the lumped-mass method and the finite element method. Figure 23: Time history result of the motion of the heave of the platform under the condition LC3. Figure 24: Time history result of the motion of the plane under the condition LC3. Hydrodynamic coefficients and wave forces are calculated by the software HydroStar. The fully coupled motion equation is solved by the software OrcaFlex. The main findings of this study are summarized as follows: Firstly, the reliability of the middle-field method to calculate the second wave force is confirmed through comparing the results of the far-field method and the middle-field method for the mean drift wave force. Secondly, the analysis of the hydrodynamic performance of the platform in regular waves reveals that the natural period of the platform is far away from the common wave period in the specific sea area where the project is located. Thirdly, when subjected to a combination of waves, winds, and currents, the maximum tension of the mooring line is found to be 2460 kN with a safety factor of 1.81 for intact survival conditions and 3337 kN with a safety factor of 1.33 for damaged survival conditions. These parameters meet the requirements guided by CCS, indicating the reliability of the designed mooring system. Furthermore, the motion of six-degree-of-freedom is deemed acceptable for the platform's operation in the specific sea area. Lastly, the net system is found to have noticeable effects on the hydrodynamic performance of the platform. Unter certain conditions, the maximum mooring line tension with nets is smaller than that without nets. The range of roll motion without nets is increased by 45% compared with the case with nets, and the range of heave motion without nets is increased by 36% compared with the case with nets. Therefore, it is recommended that the net system should be carefully considered during the design stage to ensure the platform's ability to maintain safety in severe environments. This study provides valuable insights for researchers and engineers to design and optimize this kind of semi-submersible aquaculture platform in the future. However, it is important to acknowledge several limitations of this study and identify future research directions. Firstly, the linearized potential flow models utilized in this study do not incorporate the nonlinearity caused by breaking waves. To accurately capture these nonlinear effects, advanced numerical methods such as computational fluid dynamics (CFD) simulations should be employed in future studies. Secondly, this study does not consider the installation of Sharp Eagle wave energy converters on the platform. Investigating the effects of these converters on the hydrodynamic performance of the platform should be a priority for future research. Lastly, the mooring system modeled in this study is relatively simple. Future investigations should focus on exploring more complex mooring systems to better understand their impact on the platform's performance. By acknowledging these limitations and suggesting future research directions, this study lays the foundation for continued exploration and advancement for this kind of platform. Conceptualization, W.-W.D., Y.-Z.L. and S.-W.S. ; methodology, W.-W.D., J.-Q.J. and Y.-Z.L. ; software, W.-W.D. and Y.-Z.L. ; validation, W.-W.D. and W.-Z.Y.