## 3 Experimental Setup  
In this paper, the laboratory facilities used to test the scaled model of the FOWT is a wind generator with a wind filter in front of it, a wave tank with a wave generator and a camera tracking system. A visualization of the whole laboratory setup can be seen in Figure 3.  
The wind and wave generator are installed such that the wind and wave generated are aligned. The wind generator consists of seven fans which are placed in a circular pattern. Each fan have a rated power of 4 kW. The rotational speed of fans can be controlled by an inverter, such that different wind speeds can be generated. The wind speeds which can be generated are up to 9 m/s. In front of the wind generator, a wind filter is mounted, this is designed to reduce the turbulence of the wind, straighten the wind flow, and make the wind field more uniform. The wind filter consists of three reconfigurable mesh screens, with different mesh sizes and a honeycombs screen at the outlet. The wind filter outlet have an height of 2.2 m and a width of 2.4 m. The wave tank is constructed with a shallow water depth, except at the middle where a pocket is made, which is also where the TLP is anchored to in the bottom. The wave generator is a piston type with a stroke length of 0.7 m, which is controllable through the software AwaSys [37]. It is able to generate unidirectional linear waves in the frequency range of approx. 0.2 Hz to 2 Hz. The wave generator can be set to generate regular waves, but also irregular waves according to a given wave spectrum. At the ends of the wave basin a passive wave absorber is placed, to minimize reflections. To track the movement of the TLP and tower top, an infrared camera system Prime 13 from OptiTrack was utilized. Eight cameras are placed above the wave tank in the ceiling and one relocatable camera is placed near the structure on the ground. Infrared markers are placed on the nacelle and on top of the TLP. The camera system is set to a sampling rate of 100 Hz and been calibrated such that a mean 3D error of 0.51 mm is achieved. To obtain the relative displacement of the tower top compared to the TLP the measurement of the displacement of the TLP was subtracted from the total displacement of the tower top. The scaled FOWT setup also offers the possibility to monitor the movement by  
Figure 3: Overview of laboratory facilities and experimental model. accelerometers on the wind turbine, along with the tower, and on the TLP. Furthermore, there are four sets of strain-gauges placed along the tower. For data acquisition the camera system is utilized, as this measures the displacement of the two DOF. The offshore laboratory facilities can be seen in Figure 4.  
The wind turbine of the AAUE-TLP is a 1/35 scaled model of the 5 MW NREL offshore wind turbine [38]. The wind turbine properties can be seen in Tables 1-3. The scaled FOWT was designed by utilizing geometric and Froude scaling. The scaled model of the TLP was designed on basis of work done by [PERSON] in [PERSON] (2018). The TLP is a hybrid of two reference TLP designs, these are a half-scale model of the original Sea Star oil platform [40] and a TLP inspired by the GLGH design [26], seen in Table 4. The tethers were scaled from the MIT-TLP [41] to fit the scaled spring stiffness, shown in Table 5. The tower which has the scaled flexibility and length of the 5 MW NREL offshore wind turbine tower [38]. The wind turbine is designed to operate at a wind speed from 3 m/s to 11 m/s where blades are designed to achieve the correct Froude scaled thrust force from the 5 MW NREL offshore wind turbine. The blades were then 3D printed. The wind turbine features an individual blade pitch system. In the design process of the scaled FOWT, several considerations were taken into account e.g. the fundamental frequencies of the full system, the stability during maximum external loads, the geometric size limitations of the wave tank, etc.