# The Influence of Tilt Angle on the Aerodynamic Performance of a Wind Turbine
## 4 Conclusions  
The computational fluid dynamics (CFD) method was used to simulate the aerodynamic performance of a fixed wind turbine with different tilt angles. By comparing the aerodynamic performance of a wind turbine at different tilt angles, it was found the aerodynamic performance of the wind turbine is better when the tilt angle is about 4\({}^{\circ}\). The main purpose of the paper was to study the practical importance of effect of tilt angle on the aerodynamic performance of a wind turbine. The main conclusions of the paper are as follows:  
1. In order to balance the power generation efficiency of the wind turbine and the interaction between the blade and the tower, the tilt angle of a wind turbine can be set at about 4\({}^{\circ}\) to obtain better aerodynamic performance.  
2. The increase of the tilt angle will cause the load of the section airfoil to change, thus affecting the thrust and power of the wind turbine. When the blade is located in front of the tower, increasing the tilt angle will increase the load of the section airfoil. At the same time, after the tilt angle reaches 8\({}^{\circ}\), the change in the load of the section airfoil with the tilt angle will not be obvious.  
3. Wind shear will cause the thrust and power of the wind turbine to decrease, and the effect of the wind shear exponents on the aerodynamic performance of the wind turbine is significantly greater than the expected effect of the turbulence intensity. When performing wind turbine simulations, it is recommended to use a wind shear that is closer to that found in the real environment instead of uniform wind.  
Figure 25: Thrust and power versus azimuth angle for various expected values of the turbulence intensity (\(I_{ref}\)) at \(V_{hub}=11.4\) m/s (\(\gamma=0.2\), tilt angle = 4\({}^{\circ}\)).  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Wind Shear**} & \multicolumn{2}{c}{**Average Power Pa (MW)**} & \multicolumn{2}{c}{**Average Thrust Ta (KN)**} \\ \cline{2-5}  & **Power** & **Relatively Uniform** & **Thrust** & **Relatively Uniform** \\  & & **Wind Error (\%)** & **Wind Error (\%)** \\ \hline
0.00 & 4.91 & 0.00 & 709.16 & 0.00 \\
0.09 & 4.19 & 14.66 & 677.89 & 4.41 \\
0.20 & 4.21 & 14.26 & 678.38 & 4.34 \\
0.41 & 4.30 & 12.42 & 680.64 & 4.02 \\ \hline \hline \end{tabular}
\end{table}
Table 9: The power for various wind shear exponents (\(\gamma\)) at \(V_{hub}=11.4\) m/s (\(I_{ref}=0.14\), tilt angle = 4\({}^{\circ}\)).  
In summary, in order to ensure that a fixed wind turbine has an improved aerodynamic performance, the tilt angle of the wind turbine when installed should be about 4\({}^{\circ}\). In reality, for a floating offshore wind turbine, a tilt angle of about 4\({}^{\circ}\) may not be appropriate, so the effect of tilt angle on a floating offshore wind turbine should be further studied in future works.  
Conceptualization, K.L.; Data curation, Q.W.; Formal analysis, Q.W.; Software, Q.W.; Supervision, Q.M.; Validation, Q.W.; Writing--original draft, Q.W.; Writing--review & editing, K.L. and Q.M. All authors have read and agreed to the published version of the manuscript.  
This work is supported by the National Natural Science Foundation of China (Nos. 51739001, 51779049).  
The authors declare no conflict of interest.