# Study of the Interaction between Regular Waves and a Wind-Fish Combined Structure
## 3 Results
### Wave Environmental Factors  
The hydrodynamic load of the wind-fish combined structure is an important component of the structural design, and the wave environmental factors have a significant influence on the hydrodynamic load. Therefore, it is beneficial to understand the influence of wave environmental factors on the design of the wind-fish combined structure. A total of seven wave conditions with three different wave heights, three different periods and three different water depths are set up to compare the effects of wave heights, wave periods and water depths on structural loads. Specific design parameters are shown in Table 1. The cage height \(H_{\text{net}}\) is 0.5 m, the diameter \(D_{\text{net}}\) is 2 m and the net solidity Sn is 0.27. Figures 5-7 depict the time domain curve and frequency domain diagram of the combined structure under different wave heights, periods, and water depths. It can be seen from the comparison that the horizontal wave load on the combined structure increases with the increase in wave height. The change of wave period has little effect on the horizontal wave load on the combined structure, whereas with the variation of water depth, the horizontal wave load on the combined structure increases slowly, and the wave crest occurs slightly earlier. In the frequency domain diagram, one times the frequency is inertial force, and two times the frequency is drag force. The analysis illustrates that the inertial force dominates among the three, while the drag force is weak. \begin{table}
\begin{tabular}{c c c c c c} \hline
**No.** & **Wave Height (m)** & **Period (s)** & **Water Depth (m)** & **Wave Steepness** & **Submergence Depth (m)** \\ \hline
1 & 0.10 & 1.4 & 1.0 & 0.034 & 0 \\
2 & 0.12 & 1.4 & 1.0 & 0.040 & 0 \\
3 & 0.14 & 1.4 & 1.0 & 0.047 & 0 \\
4 & 0.12 & 1.2 & 1.0 & 0.054 & 0 \\
5 & 0.12 & 1.6 & 1.0 & 0.032 & 0 \\
6 & 0.12 & 1.4 & 1.4 & 0.039 & 0 \\
7 & 0.12 & 1.4 & 1.8 & 0.039 & 0 \\ \hline \end{tabular} Note: (1) Wave conditions 1–3 are mainly used to explore the influence of different wave heights on the load of combined structures and individual structures. (2) Wave conditions 2, 4, and 5 are mainly used to explore the influence of different periods on the load of combined structures. (3) Wave conditions 2, 6, and 7 are mainly used to explore the influence of different water depths on the load of combined structures and individual structures.  
\end{table} 
Table 1: Regular wave environment parameters. Figure 5: Load duration curve and spectrum of combined structure under different wave heights. (**a**) Time domain curve. (**b**) Frequency domain diagram. In the composite structure, the sensitivity of the horizontal load on cages and wind turbines to the change of wave factor is different. In order to explore the influence of different wave factors on the safety of the combined structures, Figure 8 is the distribution diagram of the hydrodynamic load of the combined structure under different wave heights, wave periods, and water depths. Table 2 shows the proportion of the maximum horizontal load on the wind turbine foundation. Figure 8: Hydrodynamic load distribution on the combined structure under different wave heights (**a**), wave periods (**b**), and water depths (**c**). Figure 6: Load duration curve and spectrum diagram of combined structure under different periods. (**a**) Time domain curve. (**b**) Frequency domain diagram. Figure 7: Load duration curve and spectrum of combined structure under different water depths. (**a**) Time domain curve. (**b**) Frequency domain diagram. The results illustrate that with the increase in wave height, the proportion of the maximum horizontal load of offshore wind turbines gradually decreases from 94% to 88.6%, indicating that the cage has more obvious wave resistance. With the increase in the wave period, the maximum horizontal load proportion of the wind turbine foundation increases first and then decreases.