## 4 Results
### Wind Load Scenarios  
Figure 3 shows the envelopes of maximum shear forces and bending moments for the wind-only scenarios. Results corresponding to different wind velocities (5 m/s, 10 m/s, 15 m/s, 20 m/s, and 25 m/s) are plotted in different colors, while each column presents the results for the different turbulence conditions. The solid lines present the results of the time-domain multi-physics tool OpenFAST, while the dashed lines presents those of the simplified model. The results show that the maximum internal forces are found when the wind velocity is close to the rated wind velocity (around 10 m/s). The evolution of the shear forces and bending moments along the structure is similar for the three studied turbulence models. However, the influence of the wind velocity is more important for the extreme turbulence model. Comparing the results obtained with the OpenFAST software and the simplified model, similar maximum bending moments are reached through both models for the NTM and ETM turbulence levels. However, larger discrepancies are found for the extreme turbulence conditions. On the other hand, for the shear forces, significant differences are found between the simplified and multi-physics models. It is also important to note that, due to the isostatic behavior of the simplified model, shear forces and bending moments monotonically increase from the rotor to the mudline level. The envelopes of maximum internal forces obtained through OpenFAST show some oscillations that indicate dynamic effects, with the more remarkable difference being the non-zero bending moments at the hub level induced by the inertia or the rotor. Figure 2: Power Spectral Densities in the fore-aft direction obtained in parked conditions computed using the OpenFAST model. To better quantify the differences between the two considered structural models, Tables 7 and 8 present, respectively, the maximum shear forces and bending moments for the wind-only scenarios. Only results at the mudline level are included as relevant points of analysis. In each column, the values corresponding to different mean wind velocities are displayed, while the different turbulence models are sorted in groups organized by rows. These results are also presented in Figure 4, which clearly illustrates that turbulence models and wind velocities have a significant impact on the response of OWTs and on the suitability of the simplified static-equivalent model. \begin{table}
\begin{tabular}{c c c c c c c} \hline \multicolumn{2}{c}{**Wind Velocity (m/s)**} & **5** & **10** & **15** & **20** & **25** \\ \hline \multirow{3}{*}{Normal Turbulence Model (NTM)} & Simplified Model & 0.56 & 2.21 & 1.84 & 1.54 & 1.44 \\  & OpenFAST & 1.10 & 3.19 & 2.68 & 2.04 & 2.20 \\  & Difference (\%) & 48.79 & 30.77 & 31.27 & 24.67 & 34.65 \\ \hline \multirow{3}{*}{Extreme Turbulence Model (ETM)} & Simplified Model & 0.82 & 2.75 & 2.11 & 1.67 & 1.51 \\  & OpenFAST & 1.71 & 3.63 & 3.53 & 2.41 & 2.41 \\  & Difference (\%) & 51.75 & 24.46 & 40.17 & 30.66 & 37.35 \\ \hline \multirow{3}{*}{Extreme Operating Gust (EOG)} & Simplified Model & 2.78 & 5.53 & 3.35 & 2.29 & 1.87 \\  & OpenFAST & 0.86 & 2.30 & 2.37 & 2.14 & 1.85 \\ \cline{1-1}  & Difference (\%) & \(-\)223.80 & \(-\)140.91 & \(-\)41.35 & \(-\)6.98 & \(-\)1.08 \\ \hline \end{tabular}
\end{table} 
Table 7: Maximum shear forces in MN at mudline level due to wind-only scenarios. Figure 3: Envelopes of maximum shear forces and bending moments along the structure due to wind-only scenarios. As commented on before, the maximum responses are reached at wind velocities close to the rated wind velocity. This finding is consistent with the results obtained by [PERSON] et al. [6]. On the other hand, turbulence plays a crucial role in influencing shear forces and bending moments. In scenarios with low turbulence, such as the NTM or ETM, both structural models produce similar bending moments, with maximum differences of around 20%.