Efficient hydrodynamic analysis for preliminary design of Floating Offshore Wind substructures

The cost of Floating Offshore Wind (FOW) is driven by the foundation, thus it can be reduced by optimising the floater design from the early stage. Most of the numerical tools for the platform design integrate radiation–diffraction theory-based software, but it can make the whole process very time-consuming since the preliminary design phases usually imply the analysis of a large number of designs. In order to accelerate the first stages of design, and consequently, achieve the foundation cost reduction, this study proposes an efficient methodology for the hydrodynamic added mass, radiation damping, and excitation loads calculation. The method is implemented for a semi-submersible platform, and it is verified against the radiation–diffraction commercial software AQWA. The methodology is validated through a comparative analysis of the response of ten different platforms, and it has shown that the hydrodynamic coefficients derived from either radiation–diffraction analysis or from the proposed method lead to equivalent conclusions. The maximum values of the platform's pitch angle and the nacelle acceleration are assessed, achieving a maximum deviation among the most critical designs of 3% and 17%, respectively. This methodology has demonstrated to provide with reasonable accuracy the dynamic behaviour of the offshore wind substructures achieving a significant computational cost reduction compared to the state-of-the-art methods, which enables to accelerate the optimisation process and thus, resulting in a more accurate floater preliminary design.