## 4 Results
### Aerodynamic Load  
A set of experiments with only the aerodynamic load is conducted, there are no generated waves present. This is to see the aerodynamic loads effect on the dynamics of the tower and TLP. There are conducted three experiments at three different mean wind speeds: 6 m/s, 7 m/s and 8.6 m/s. The rotational speed will be set to the scaled operational rotational speed at the given wind speed, which is 68 RPM, 71.5 RPM, and 71.5 RPM, respectively. It should be noted that in the simulations a closed loop manually tuned PI controller was used to regulate the generator torque, to keep the constant reference speed. In the experiments a variable 3-phase load was manually set prior to the experiment, such that the reference speed was achieved. Each experiment was carried out for 10 min, while the simulation time was 5 min. The wind field conditions in the experiment have been found by conducting measurements at multiple wind speed, at multiple points in the wind field. Figure 7: **(a)** Experimental time series data of the surge displacement of the TLP, when exposed to waves generated from a scaled down JONSWAP wave spectrum. **(b)** Experimental time series data of the surge displacement of the tower top, when exposed to waves generated from a scaled down JONSWAP wave spectrum. The wind field data was analyzed to generate a mean wind speed field and multiple PSDs at different points in the wind field. These were then used to generate a 3D wind simulation. The 3D wind simulation consist of a turbulent wind field time series at multiple discrete points in the wind field. These was calculated by the method presented by [PERSON] [45]. To generate the wind field time series for FAST, TurbSim was utilized. In TurbSim only a single turbulence model can be used to describe the wind fields PSD. To resolve this, a mathematical turbulence model was fitted to the mean of the experimental found PSDs of the wind field. The mean wind speed field in FAST also differs from the experimental, as this was not able to configure manually. It should be noted that the wind speed was ramped up from 0 m/s to the reference mean wind speed, in both the experiment and the theoretical model, but this was not possible to do in Turbsim. Therefore, the data from an initial period of 100 s in the experiments and simulations were disregarded in the analysis. A time series of the TLP and tower top displacement at a mean wind speed of 7 m/s, from the experiment can be seen in Figure 9.  
As the wind field generated in the experiments and the simulations are not the same in the time domain, not much information can be drawn from direct comparison. But by investigating the mean  
Figure 8: (**a**) The PSDs of the displacement of the TLP, when exposed to waves generated from a scaled down JONSWAP wave spectrum. (**b**) The PSDs of the displacement of the tower top, when exposed to waves generated from a scaled down JONSWAP wave spectrum. Figure 9: (**a**) Experimental time series data of the displacement of the TLP at a wind speed of 7 m/s. (**b**) Experimental time series data of the displacement of the tower top at a wind speed of 7 m/s. and variance of the time series from the experiments and simulations some observations can be made about the simulations. The mean and variance for the different experiments can be seen in Table 6.  
From Table 6, it can be seen that mean displacement offset of the TLP from the theoretical model and FAST are overestimated compared to the experimental data. The theoretical model and FAST both have a larger standard deviation of the displacement. The discrepancy in the standard deviation can be due to the damping of the TLP. The damping of the TLP was calibrated to fit when only hydrodynamic loads were present, for more information see [24]. Therefore, an identification of the change in damping of the TLP when an aerodynamic load is applied should be conducted. This is out of the scope for this paper.