## 6 Summary and Conclusions  
High-resolution simulation of the Typhoon \"Nuri\" was accomplished based on the mesoscale WRF model. Later, differences regarding the aerodynamic force, wind-induced responses, buckling stability, and ultimate bearing capacity of the wind turbine system under normal wind and typhoon loads were analyzed by microscale CFD numerical simulation and the finite element method. Some major conclusions could be drawn:  
* A high-resolution simulation of Typhoon \"Nuri\" was carried out through the mesoscale WRF model. The typhoon profile index that was based on the least square fitting was 0.118, which was about 20% smaller than the wind profile index under normal wind loads. In this paper, the meso/microscaled nested downscaling method can effectively simulate a three-dimensional typhoon field of similar structures and provide effective input loads for follow-up comprehensive stress analysis. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Buckling Eigenvalue under** & \multicolumn{2}{c}{**Buckling Mode**} & \multicolumn{2}{c}{**Buckling Mode under**} & \multicolumn{2}{c}{**Buckling Eigenvalue under**} \\
**Normal Wind** & \multicolumn{2}{c}{**under Normal Wind**} & \multicolumn{2}{c}{**Typhoon Loads**} & \multicolumn{2}{c}{**Typhoon Loads**} \\ \hline Buckling coefficient & 2.955 & & & Buckling coefficient & 2.992 \\ Critical wind & 24.12 & & & Critical wind & 31.57 \\ speed/(m/s) & & & & speed/(m/s) & \\ Maximum displacement/m & 0.025 & & & Maximum displacement/m & 0.032 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Comparison of buckling mode and eigenvalues of wind turbine system under normal wind and typhoon loads. Figure 24: Changes of the buckling displacement of the wind turbine with wind speed under normal wind and typhoon loads. * The flow field distribution surrounding the wind turbine is basically similar under normal wind and typhon effects. However, the airflow under typhoon conditions showed higher wind speed and turbulence compared with those under normal wind. Positive pressure on windward surface of the tower body, negative pressure on the crosswind surface of the tower body, the overall pressure coefficient of the blade, the resistance coefficient of the tower body, and the coupling structural response all increased significantly. The buckling stability and ultimate bearing capacity of the coupling system decreased significantly. * The pressure coefficient on the windward surface of the tower body under typhoon conditions increased by 61.1% to the maximum extent. The maximum increment of the negative pressure extremum on the crosswind surface was 44.9%. Both were observed at the bottom of the tower body. The typhoon influenced the pressure coefficient on the windward surface of the blades significantly, but it only affected the leeside surface slightly. The maximum increment of the overall pressure coefficient of the blade was 23.6%, which occurred at the tip of Blade C. Under typhoon conditions, the resistance coefficient of the tower body increased significantly, and the maximum increment, 67.5%, occurred at the bottom of the tower body. * Under typhoon conditions, the radial displacement at the tower top of the wind turbine increased by 28.6%. The increments of the maximum meridian axial force, maximum shearing force, maximum circumferential bending moment, and maximum meridian bending moment were 36.1%, 34.8%, 34.2%, and 46.5%, respectively. All were observed close to the circumferential 330\({}^{\circ}\). The maximum increments of the shearing force, circumferential bending moment, and meridian bending moment at the blade root under typhoon conditions were 41.3%, 39.6%, and 39.5%, which were observed on Blade C. The maximum increment of downwind displacement at the blade tip occurred on Blade A, which reached 49.3%. * Under typhoon conditions, the buckling coefficient, critical wind speed, and maximum buckling displacement of the wind turbine system increased by 1.3%, 30.9%, and 28%, respectively.