# Numerical Study on Hydrodynamic Performance of a New Semi-Submersible Aquaculture Platform
## 1 Introduction
[PERSON] et al. [15] introduced a new net cage with a shielding device and analyzed its hydrodynamic characteristics using a numerical method based on computational fluid dynamics. The gravity cages with floating collars and flexible nets mentioned above suffer from large cage deformation at offshore sites with high sea states. It is urgent to develop aquaculture facilities in typical offshore environments to overcome this. Various innovative concepts of aquaculture facilities have been developed recently by combining technologies from the offshore industry with fish farming. Correspondingly, researchers have conducted a series of numerical and physical experimental studies to evaluate and enhance the hydrodynamic performance of these structures. Ocean Farming AS, a subsidiary of the SalMar Group, developed the world's first offshore fish farm, Ocean Farm 1, which is dodecagonal in shape. It has a height of 68 m, a diameter of 110 m, and a volume of 250,000 m\({}^{3}\)[16]. [PERSON] [17] conducted hydrodynamic analysis of Ocean Farm 1 in both frequency and time domains using the HydroD V4.10 and SIMA V4.1 software packages, respectively. [PERSON] et al. [18] modeled Ocean Farm 1 using SIMO/RIFLEX/SIMA V4.1 software packages and investigated its motion responses under different combined conditions of irregular waves and currents. [PERSON] et al. [19] assessed the structural strength of Ocean Farm 1 under supply vessel collisions using the nonlinear finite element program USFOS. [PERSON] et al. [20] presented a semi-submersible offshore fish farm similar to Ocean Farm 1 and conducted a series of physical model experiments to investigate its motion response and mooring line tension. [PERSON] et al. [21] analyzed the hydrodynamic characteristics of an aquaculture platform similar to Ocean Farm 1 in uniform currents using the porous media combined with a rigid wall based on the SST k-omega turbulence model. NSK Ship Design for a Norwegian fishing company designed a novel vessel-shaped fish farm, Havfarm 1, which consists of a vessel-shaped floater, five flexible cages under the floater, and a single point mooring system, with a total length of 385 m [22]. [PERSON] et al. [23,24]analyzed the global responses of Havfarm 1 and the tensions in the mooring lines under various wave and current conditions using the coupled SIMO-RIFLEX V4.1 computer program. [PERSON] et al. [25] proposed an integrated method to predict the misalignment angle between the heading of the vessel-shaped offshore fish farm and the incoming currents under combined waves and currents, to facilitate the design of the dynamic positioning system used for the fish farm. [PERSON] et al. [26] proposed an optimization methodology for mooring system design and designed the mooring system of the vessel-shaped offshore fish farm accordingly. [PERSON] et al. [27] presented a single-point moored vessel-shaped floating aquaculture platform with two different steel floating frames, nets, and weight system pipes and analyzed its motion, mooring force, and net reaction force in regular waves using the boundary element method and the lumped mass method. [PERSON] et al. [28] depicted a hinged multi-body floating aquaculture platform with square floating frames, nets, and weight system pipes and examined the effects of the hinge joint rotational stiffness on its dynamic responses under different wave steepnesses using the boundary element method and the lumped mass method. Ocean University of China and Hubei Ocean Engineering Equipment Research Institute co-designed China's first fully submersible deep-sea fish farm, ShenLan 1. The farm features a rigid frame with eight vertical columns, two cylindrical liquid-gas tanks, and ultra-high-strength polyethylene square nets. The full-scale diameter and height are 60.44 m and 34.45 m, respectively [29]. [PERSON] et al. [30,31] used the open-source CFD toolbox REEF3D to analyze the effects of the wave parameters and structural variations on the response motions and mooring forces of ShenLan 1. [PERSON] et al.