## 4 Results
### Aerodynamic and Hydrodynamic Load  
To see the effect of simultaneous wind and wave loading, a series of test was conducted. The FOWT was tested at three different wind speeds simultaneously with monochromatic waves at two different frequencies. The FOWT was tested at a mean wind speed of 4 m/s, 7 m/s and 8.6 m/s, where the rotor speed reference was set to 41.5 RPM, 71.5 RPM and 71.5 RPM, respectively. The wave height was set to 0.01 m and the wave frequency was set to 0.6 Hz and 1.7 Hz. Thus six test was conducted in total, each of the experiments was conducted for 10 min, while the simulation time was set to 5 min. A time series of the displacement in surge of the TLP and tower top from one of the tests can be seen in Figure 11.  
By analyzing the time series data from the experiments and simulations some observations about the mean displacement and the standard deviation of the oscillations. These can be seen in Tables 7 and 8. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline  & & \multicolumn{3}{c}{**4 m/s**} & \multicolumn{3}{c}{**7 m/s**} & \multicolumn{3}{c}{**8.6 m/s**} \\ \cline{3-8}  & & \(\mu\) **(mm)** & \(\sigma\) **(mm)** & \(\mu\) **(mm)** & \(\sigma\) **(mm)** & \(\mu\) **(mm)** & \(\sigma\) **(mm)** \\ \hline \multirow{3}{*}{TLP} & Experiment & 7.2 & 3.2 & 21.4 & 3.3 & 20.9 & 3.7 \\  & FAST & 10.7 & 3.2 & 31.5 & 5.4 & 32.4 & 4.2 \\  & Theoretical & 9.9 & 3.1 & 35.0 & 3.9 & 32.7 & 4.1 \\ \hline \multirow{3}{*}{Tower Top} & Experiment & 2.6 & 1.1 & 8.6 & 1.8 & 7.5 & 2.0 \\  & FAST & 2.3 & 0.7 & 7.6 & 1.0 & 7.2 & 1.7 \\ \cline{1-1}  & Theoretical & 3.1 & 0.9 & 11.2 & 1.5 & 9.8 & 1.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: The mean (\(\mu\)) and standard deviation (\(\sigma\)) of the displacement in surge of the TLP and tower top at simultaneous wind and wave loading. The wind speeds which is tested at is 4 m/s, 7 m/s and 8.6 m/s and monochromatic waves with a wave height of 0.01 m and wave frequency of 0.6 Hz. Figure 11: (**a**) Experimental time series data of the displacement of the TLP at a wind speed of 7 m/s and monochromatic waves with a wave height of 0.01 m and wave frequency of 0.6 Hz. (**b**) Experimental time series data of the displacement of the tower top at a wind speed of 7 m/s and monochromatic waves with a wave height of 0.01 m and wave frequency of 0.6 Hz. By inspection of the mean displacement of the TLP in both tests in Tables 7 and 8, it can be seen that the simulations overestimates this compared to the experiments. This occurs due to the same reasons as mentioned in Section 4.3. Furthermore, it can be seen that the mean displacements of the TLP and tower top inboth the experiments and simulations, do not differ much from tests with only the aerodynamic load, seen in Table 6.  
The standard deviation of the oscillations of the TLP in the experiment and simulations at the applied wave frequency of 0.6 Hz is in good agreement. While at the applied wave frequency of 1.7 Hz, the standard deviation of the experimental oscillations is lowered by a great amount. This is not captured in the simulations, as both models overestimates the oscillations. The mean displacement of the tower top fits quite well with FAST, while the theoretical model seems to overestimate the mean displacement. The tower tops displacement in the theoretical model has a tendency to overestimate the mean offset, while FAST seems to have fit better with the experiments. The standard deviation of the oscillations of the tower top in the experiment and simulations at both wave frequencies is in good agreement. Though, the standard deviation in FAST fits well at the low wave frequency of 0.6 Hz, while at the higher wave frequency of 1.7 Hz it seems to underestimate the oscillations. By comparing the experimentally calculated mean and standard deviation of the displacement in surge at the two different wave frequencies. It can be seen that the mean displacement for both the TLP and tower top do not differ.