# Numerical Modelling of a Floating Wind Turbine Semi-Submersible Platform
## 4 Conclusions  
In this article, we have focused on the process of the first steps to analyse floating platforms for offshore wind, aiming to start a whole computational simulation of the design and verification process for this type of structures. We started with mesh and time dependency studies, and then we analysed a few of the first steps needed for this type of structures, such as decay tests and regular wave tests. To be able to compare the numerical modelling, the motion obtained from experimental tests in the LIR/NOTF wave basin by Saitec Offshore Technologies was used as the ground truth. The main aim of this study was to consolidate a good basis for both hydrodynamic and computational understanding of this type of simulations before proceeding to more complex steps such as towing tank testing including regular and irregular wave tests. Figure 10: Damping factor study between the experimental and computational tests with linear fitting of both. Figure 9: Signal comparison of the experimental (blue) and computational (orange) decays with the interaction of mooring systems. Throughout the process, three DoFs were locked due to the limitations of the use of a symmetry plane. However, this implementation allowed us to decrease the computational weight of each of the simulations is half. Because of that, only heave, surge and pitch DOFs were used. The coupling study, adding a mooring system in the decay tests and the regular wave tests, showed good relations between the experimental and computational results. Although the results shown in the study are promising, some clear improvements can be made in future research to close the differences shown in our comparisons. The damping in the simulations at low velocities, peaks and droughts is lower in the computational runs than in the experimental ones. This is related to the dynamic viscosity, which should vary with the movement of the platform instead of being considered constant. We believe that the difference is more visible in a platform like the studied one with a complex geometry. The first half-period of the simulations has a greater discrepancy in time due to the damping, because in those first moments the damping of the platform is lower in the computational domain. However, this does not imply that we are underestimating the hydrodynamic damping but may be directly related to the lock of various DoFs, defining the hydrodynamic damping in those DoFs. Although the application of the symmetry plane is commonly used for this type of research, the lock of three DoFs may be directly related to the hydrodynamic damping of the platform, which allows the researchers some margin of error. Moreover, the existence of sensors in the experimental prototype imposes a small difference in its behaviour that cannot be simulated. In future research, more detailed analysis will be conducted on the decay testing, and the mesh and time dependency studies will be extended to regular and irregular waves, as well as to currents and towing tests, which are of great importance for this type of structures. Finally, the simulations show promising results, and the researchers feel positive regarding the implementation of this type of simulations in industrial processes, which can be of great help when studying the behaviour of platforms taking into consideration the non-linearity with greater detail. Conceptualization, L.G.-C.; methodology, validation, G.I. ; formal analysis, J.M.B. and G.I. ; data treatment, L.G.-C.; writing--original draft preparation, L.G.-C.; writing--review and editing, J.M.B. and G.I. ; supervision, J.M.B. and G.I. All authors have read and agreed to the published version of the manuscript. The current investigation was developed under the framework of the European Regional Development Fund through the \"Interreg Atlantic Area Programme\" under contract EAPA 344/2016, providing experimental inputs to complete this study. Not applicable.