Sustainable and renewable energies are essential in achieving climate targets set by the Paris Agreement and Sustainable Development Goals (SDGs). Floating offshore wind turbines (FOWTs) represent an innovative technology with considerable potential to contribute to these goals. However, being a relatively new technology, FOWTs pose challenges that must be addressed to enhance their development. To speed up FOWT installation and optimize their design, accurate numerical simulation tools are essential, particularly mid-fidelity models, which use less computational time but require precise hydrodynamic characteristics to be tuned. These tuning parameters are obtained with experimental tests or with Computational Fluid Dynamics (CFD) simulations.
This thesis aims to analyze the added mass and drag coefficients of the MaRINET2 semi-submersible wind turbine floater when subjected to forced oscillatory motion, utilizing a validated CFD model. To achieve the objective, a nonlinear Navier Stokes numerical model was developed within the open-source CFD software OpenFOAM. The interFoam solver was employed for the simulations. A mesh convergence study identified an optimal mesh configuration, balancing computational efficiency with result accuracy. Two types of simulations were conducted: free decay simulations for model validation against University of Strathclyde (UoS) experimental data and forced oscillatory simulations to compute added mass and drag coefficients under varying oscillation parameters.
It was found that heave added mass is sensitive to both oscillation amplitude and period, while heave drag coefficients displayed minimal influence at shorter periods. For high-amplitude oscillations, surge drag coefficients remained stable across oscillation periods, yet longer periods increased coefficients for
mid and low amplitudes. Pitch added mass coefficients remained unaffected by oscillation amplitude but increased with longer periods. Comparing these hydrodynamic parameters with two reference papers revealed both similarities and discrepancies in trends. It is challenging to attribute these discrepancies
only to floater geometry due to the lack of specific experimental data for this floater.