## 4 Numerical Simulation
### Sensitivity Analysis of Accessory Combination Usage Parameters  
According to the above comparative analysis, it can be concluded that the parameters with the best optimization effect on the mooring system when the buoy and the weight are used alone. In order to find the best combination of parts to optimize the overall response of the floating wind turbine, and to verify that there is no influence between the mooring parts, the control variable method is used to verify. After changing one of the parameters, compare it with the optimal solution. The specific solution is shown in Table 6. Using SIMA to simulate the motion response of the floating wind turbine under extreme sea conditions for 3 h under different parameter combinations of mooring accessories, the motion response and tension statistics of the floating wind turbine are obtained. Figure 9 is the comparison chart of the motion response and tension of the floating wind turbine when the accessories are combined. In order to make the comparison result more clearly visible, the relatively stable 5800-6000 s of the 10,800 s time history response curve of the floating wind turbine in the time domain is selected for comparison, as shown in Figure 10. Case 2-Case 5 are the schemes after changing a mooring accessory parameter in Case 1, and Case 6 is the scheme without mooring accessories. The comparison with Case 6 shows that the combination of accessories has a significant effect on the optimization of the response of the floating wind turbine, while the comparison with Case 1 shows that the optimization effect of Case 1 is better than the other solutions, which means that the combination of accessories does not affect the optimization law of the mooring system when the accessories are used alone. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Case**} & **Buoy** & **Buoy** & **Mass of Clump** & **Clump Weight** \\  & **Volume/m3** & **Position/m** & **Weight/kg/m** & **Location/m** \\ \hline Case1 & 10 & 15 & 900 & 62.13 \\ Case2 & 20 & 15 & 900 & 62.13 \\ Case3 & 10 & 25 & 900 & 62.13 \\ Case4 & 10 & 15 & 700 & 62.13 \\ Case5 & 10 & 15 & 900 & 112.13 \\ Case6 & – & – & – & – \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Combination scheme of accessories. Figure 8: Comparison diagram of tension of No. 2 mooring line under different parameters of clump weight. (**a**) Different quality. (**b**) Different positions Heave. Figure 10: Comparison diagram of time history curve of floating wind turbine with different parameter and fitting combination. (**a**) Surge. (**b**) Heave. (**c**) Pitch. (**d**) Tension. Figure 9: Comparison diagram of response of floating wind turbine with different parameter and fitting combination. (**a**) Surge. (**b**) Heave. (**c**) Pitch. (**d**) Tension. In order to further explore whether the mooring accessories will improve the performance optimization effect of mooring system when the mooring accessories are used in combination compared with the accessories alone, the percentage of performance improvement of the mooring system after the parameters are changed when the accessories are used in combination is calculated, and the change is the same as when the accessories are used alone. The percentage of mooring performance improvement after fitting parameters is compared, as shown in Figure 11. In the figure, we can see that although the difference in the improvement rate of mooring performance by changing some of the parameters is small, on the whole, changing the parameters of the accessories when the accessories are used in combination has a greater impact on the performance of the mooring system than changing the same parameters when using the accessories alone. And I can see from the graph that the points where the difference is smaller are generally concentrated when changing the mass of the clump weight.