## 4 Results and Discussion
### Influence of Turbulence Intensity on Aerodynamic Performance of Wind Turbines
#### 4.2.2 Effect of Turbulence Intensity on Structural Response
Table 10 shows the statistical table of the mean, maximum and standard deviation of the blade tip displacement curves during this period. From Table 10 and Figure 23, it can be seen that for the flapping direction, the mean, maximum and standard deviation of the blade tip displacement increase significantly with the increase in turbulence intensity when the reference wind speed is 10.0 m/s. The blade deformation caused by turbulence intensity cannot be ignored. When the blade is under irregular load for a long time, the presence of fatigue must be taken into account. It is also necessary to adjust the windward area of the blade in real time by variable blade control to ensure that the blade vibration does not change drastically in a short period of time. From Figure 24, it can be seen that at a wind speed of 10 m/s, the stress distribution concentration on the blade surface becomes more and more obvious with the increase in turbulence intensity. Under uniform wind speed, the stress concentration in the middle of the blade is basically connected to a piece. However, with the increase in turbulence \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{
\begin{tabular}{c} **The Intensity of** \\ **Turbulence** \\ \end{tabular} } & \multicolumn{3}{c}{**Tip Displacement-Flapping Direction/m**} \\ \cline{2-4}  & **The Average** & **The Maximum** & **The Standard Deviation** \\ \hline uniform & 4.782 & 4.795 & 0.029 \\
5\% & 4.845 & 5.066 & 0.141 \\
10\% & 4.958 & 5.553 & 0.196 \\
15\% & 5.023 & 5.781 & 0.240 \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Parameter setting of turbulent wind field for wind turbine calculation. Figure 23: Statistical characteristics of blade tip displacement curve. intensity, the blade is affected by turbulence, the pressure distribution on the blade surface appears to be concentrated in a few areas, which has a higher requirement for the local compressive performance of the blade, and also challenges the bonding ability of the outer surface skin material of the blade. From Figure 25 and Table 11, it can be observed that the stress on the blade surface and web increases with the increase in turbulence intensity, and the stress increment between adjacent working conditions keeps increasing, which demonstrates that the stress concentration degree on the blade is increasing. Under the action of turbulent wind, the blade surface will have a sudden stress concentration phenomenon since the wind load changes suddenly. This is a challenge for the blade local (15% of the length from the blade root) stresses, where additional protection is needed to avoid damage to the blade skin material and internal structure. Figure 24: Stress distribution on the blade surface under different turbulence intensities. (**a**) Stress distribution on blade surface under uniform wind. (**b**) Stress distribution on blade surface under 5% turbulence intensity. (**c**) Stress distribution on blade surface under 10% turbulence intensity. (**d**) Stress distribution on blade surface under 15% turbulence intensity. Figure 25: Statistics of blade surface stress.