# Numerical Simulation of Fluid-Structure Coupling for a Multi-Blade Vertical-Axis Wind Turbine
## 4 Results and Analysis
### Pressure Field Analysis  
It can be seen from the equivalent pressure field distribution of the blade surface in Figure 8 that, under the same wind speed, the maximum pressure in the overall structure appears in the variable angle position of the blades in the windward region. This is mainly due to the rapid airflow changes, complex turbulence, and significant impact of the wind field on the blade in this region, making the blade prone to bending or damage. Furthermore, it can be found that the equivalent pressure on the surface of four-blade and six-blade wind turbines is significantly higher than that on five-blade and three-blade wind turbines under the same external wind field environment. The maximum equivalent pressure of six blades can be reached at 3.161 \(\times\) 10\({}^{6}\) Pa. The maximum blade surface pressure of a five-blade wind turbine is 3.5607 \(\times\) 10\({}^{5}\) Pa.  
Figure 8: _Cont._  
Figure 7: Import pressure of the blades. Figure 8: Vane variable distribution map of different wind turbines: (**a**) three blades; (**b**) four blades; (**c**) five blades; (**d**) six blades. To analyze the pressure distribution on the blade, the center line of the blade is taken as the reference line to analyze and observe the pressure distribution on the reference line. The simulation diagram is shown in Figure 9.  
Table 2 shows eight equidistant reference points from top to bottom. Figure 10 shows the pressure distribution trends of different blade reference lines. It can be seen that the pressure of the four-blade and the six-blade is relatively large, and the pressure distribution of the six-blade changes greatly, which can easily cause the deformation of the blade due to uneven pressure distribution. In comparison, the pressure of three blades and five blades is smaller, and the distribution of pressure is more uniform. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Fan Type** & **Point 1** & **Point 2** & **Point 3** & **Point 4** & **Point 5** & **Point 6** & **Point 7** & **Point 8** \\ \hline three-blade & \(6.23\times 10^{5}\) & \(5.76\times 10^{5}\) & \(4.75\times 10^{5}\) & \(4.02\times 10^{5}\) & \(3.62\times 10^{5}\) & \(3.58\times 10^{5}\) & \(4.90\times 10^{5}\) & \(5.01\times 10^{5}\) \\ four-blade & \(1.33\times 10^{6}\) & \(1.38\times 10^{6}\) & \(1.41\times 10^{6}\) & \(1.42\times 10^{6}\) & \(1.41\times 10^{6}\) & \(1.43\times 10^{6}\) & \(1.38\times 10^{6}\) & \(1.37\times 10^{6}\) \\ five-blade & \(7.92\times 10^{5}\) & \(6.61\times 10^{5}\) & \(4.22\times 10^{5}\) & \(2.41\times 10^{5}\) & \(1.61\times 10^{5}\) & \(1.34\times 10^{5}\) & \(1.68\times 10^{5}\) & \(3.93\times 10^{5}\) \\ six-blade & \(2.49\times 10^{6}\) & \(1.80\times 10^{6}\) & \(1.38\times 10^{6}\) & \(1.05\times 10^{6}\) & \(1.15\times 10^{6}\) & \(1.34\times 10^{6}\) & \(1.74\times 10^{6}\) & \(2.63\times 10^{6}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Equivalent pressure gauge at different measuring points of blade. Figure 10: Trend map of stress distribution of different blade reference lines. Figure 9: Leaf reference line schematic diagram. As shown in Figure 10 and Table 2, the equivalent pressure distribution curve at different measurement points on the three blades has a gentle trend, and the maximum value is 6.23 \(\times\) 10\({}^{5}\) Pa, while the minimum value is 3.58 \(\times\) 10\({}^{5}\) Pa. The distribution curve of the four blades has small local fluctuations, the overall trend is gentle, and the maximum value is 1.43 \(\times\) 10\({}^{6}\) Pa, while the minimum value is 1.33 \(\times\) 10\({}^{6}\) Pa. The pressure distribution curve of the five blades decreases slowly at first and then rises slowly with the increase of the measurement point value, and the maximum value is 7.92 \(\times\) 10\({}^{5}\) Pa, while the minimum value is 1.34 \(\times\) 10\({}^{5}\) Pa.