Second-order Diffraction Forces on a Vertical Cylindrical Body Using Theoretical, Numerical Formulations and CFD Approaches Available to Purchase

The forthcoming development of Floating Offshore Wind Turbine (FOWT) farms due to the expansion of the renewable energy sector requires further investigation of certain aspects. A FOWT system includes dynamic subsea power cables that are prone to fatigue and require a solid assessment of the action of hydrodynamic loads mainly due to the FOWT displacements. This paper addresses the computation of second-order diffraction forces acting on a vertical cylindrical structure, which can be regarded as a support for FOWT, in a finite water depth. It presents a semi-analytical formulation for solving the first-order diffraction problem utilizing the macroelement approach. The derivation of the second-order forces is achieved by employing Green’s second identity in conjunction with an auxiliary first-order radiation potential. The present work investigates and quantifies the limits of each method. Furthermore, the results obtained from the theoretical analysis are supplemented and compared with those derived from numerical software and a high-fidelity Computational Fluid Dynamics simulation, aimed at assessing the limitations of both analytical and numerical solvers in evaluating the second-order oscillatory loads exerted on the structure.