# Numerical Study on Hydrodynamic Performance of a New Semi-Submersible Aquaculture Platform
## 1 Introduction  
As the global population and economy continue to grow, human demand for aquaculture products increases rapidly, and natural fishery resources decline drastically. Aquaculture farms play an increasingly important role in avoiding overfishing of aquatic products. However, aquaculture farms in inhomore and harbor areas are facing limited development and receiving increased criticism due to the lack of production sites and the adverse impact on local ecosystems [1]. In contrast, moving aquaculture farms to the offshore seas is a popular and inevitable trend due to the broader development space, better water quality, and stronger environmental purification capacity in more exposed sea regions [2]. Nevertheless, aquaculture facilities in open seas will endure much more severe environmental conditions. The hydrodynamic performance of aquaculture facilities is a crucial factor that affects their stability, safety, and economy. Evaluating the hydrodynamic performance of these structures has important theoretical and practical significance for their design, optimization, and management. Therefore, the design and development of aquaculture facilities with excellent hydrodynamic performance can significantly support the advancement of offshore aquaculture technology. Surface floating gravity-type cages have been widely used in fish farming in the past decades due to their large breeding capacity and simple daily maintenance compared with other types of cages. Researchers have widely investigated the hydrodynamic characteristics of this kind of cage and its components, such as the floating collar, the net system,and the mooring system, through numerical simulations and physical models. [PERSON] et al. [3] studied the dynamic characteristics of a central spar fish cage deployed in the Gulf of Marine using physical and numerical models. [PERSON] and [PERSON] [4] investigated the dependency between the forces and the geometry of a flexible circular net cage with different sizes of bottom weights in a flume tank by measuring the global forces and net deformation. [PERSON] et al. [5] developed a numerical model to analyze the motion response and the mooring forces of a gravity cage in a combined wave-current flow and found that the numerical results agreed well with the experimental data. [PERSON] et al. [6] utilized a previously validated numerical model to examine the effects of waves and currents on the tension of mooring lines and volume reduction of two types of gravity net cages: a double-cage system and a single-cage system. [PERSON] et al. [7] proposed a numerical model based on statistical approaches and Fourier transforms to analyze the motion response and mooring line tension of gravity cages in irregular waves. [PERSON] et al. [8] studied the floater motion and the net volume reduction of a gravity net cage in waves and currents using the finite element method and the buoyancy distribution method. [PERSON] et al. [9] investigated the nonlinear hydroelastic response of a deep-water gravity fish cage in irregular waves using the finite element method and the modal superposition method. [PERSON] et al. [10] proposed a self-submersible single-point-mooring cage concept and investigated its submergence characteristics in regular waves with following currents using the numerical model Aqua-FE. [PERSON] et al. [11] further investigated its submergence characteristics in random waves. [PERSON] and [PERSON] [12] studied the hydrodynamic response of a cage system with a flexible surface collar, net, ballast, and mooring lines in regular/irregular waves and currents using a Morison-force model and validated it with experimental data. [PERSON] et al. [13] investigated the mooring loads of a realistic aquaculture fish farm system with a floating collar, a flexible net cage, and a sinker tube using a reliable numerical tool and validated it with experimental data. [PERSON] et al. [14] numerically studied the mooring forces of a fish cage array with six gravity cages in currents and waves using the finite element method.