## 2 Materials and Methods
### Establishment and Validation of the Numerical Model  
The geometric and material parameters of the SPM-GDW cage system are listed in Table 1. Based on the real cage parameters provided, the numerical model of the SPM-GDW cage was established in OrcaFlex, as shown in Figure 4 below. \begin{table}
\begin{tabular}{c c c} \hline
**Component** & **Parameters** & **Values** \\ \hline \multirow{4}{*}{Floating collar} & Pipe diameter/mm & 400 \\  & Wall thickness/mm & 23.5 \\  & Length/m & 20 \\  & Material & HDPE \\  & Yield strength/MPa & 26 \\ \hline \multirow{4}{*}{Net} & Mesh size/mm & 45 \\  & Twise diameter/mm & 2 \\  & Height/m & 6 \\  & Material & UHMWPE \\ \hline \multirow{4}{*}{Mooring line} & Length/m & 60 \\  & Diameter/mm & 40 \\  & Breaking strength/kN & 153 \\  & Material & PE \\ \hline \multirow{2}{*}{Anchor} & Type & AC-14 \\  & Weight/kg & 1575 \\ \hline \multirow{2}{*}{Buoy} & Height/m & 2 \\  & Diameter/m & 1.5 \\ \hline \multirow{2}{*}{Sinker} & Weight/kg & 20 \(\times\) 20 \\  & Material & Concrete \\ \hline \end{tabular}
\end{table} 
Table 1: Parameters of the SPM-GDW net cage. Figure 4: Numerical model of the novel SPM-GDW net cage in OrcaFlex. The numerical model was verified by the physical model tests of the cage conducted in the wave tank at Jiangsu Rudong Experimental Base of the Chinese Academy of Fishery Sciences [26; 29]. Considering the actual net cage size, wave tank conditions, and the model cost, among other factors, the model scale was set to 1:15. The tests investigated the dynamic response characteristics of the cage under different pure wave and combined wave-current conditions. These results were then compared with the numerical simulation results. It was noted that the AC-14 high-holding power anchor was adopted in the novel SPM-GDW net cage. But considering the limitations in the cage numerical model and experiment, the actual anchor was not created, and the anchor point was arranged as fixed instead. And due to limitations in experimental conditions, only the physical model tests on the dynamic response of net cages under regular waves were conducted. Thus, the validation of the numerical model of the net cage was also based on regular waves. The experimental configuration of the novel SPM-GDW is shown in Figure 5. The measuring point was fixed to the cage, and the 6 DOFs (degrees of freedom) motion was measured using the 3D motion capture system. A wave height gauge and a current meter were arranged to monitor the wave height and current velocity, respectively. A strain-type tension gauge was adopted to measure the mooring line tension. Considering the capacity of the wave-current generation system and the test conditions of the water tank, the regular waves with different heights (16 cm, 20 cm, 24 cm), periods (1.64 s, 2.01 s), and current velocities (10.3 cm/s, 12.9 cm/s) in the experiment were set as the environmental conditions. Three pure regular wave conditions (H = 16 cm, 20 cm, 24 cm; T = 1.64 s) were selected for comparative verification of motion response. Figure 6 shows the motion response comparison of the novel SPM net cage between the numerical model and experiment is not significant. The maximum error on heave motion is 11.7% (H = 20 cm, T = 1.64 s), and the maximum error on pitch motion is 9.4% (H = 24 cm, T = 1.64 s). The comparison results are reasonable and acceptable due to inevitable factors in numerical simulation. Two regular waves combined with current conditions (H = 16 cm, T = 1.64 s, U = 10.3 cm/s; H = 24 cm, T = 2.01 s, U = 12.9 cm/s) were selected for comparative verification of mooring tension. Figure 7 shows the mooring tension comparison of the novel SPM net cage between the numerical model and the experiment. The comparison shows that due to a possible test data-gathering error, the numerical simulation results on mooring tension were not perfect to catch the experimental results. But in terms of extreme values of mooring tension, it was acceptable.