Resonant response of a flexible semi-submersible floating structure: experimental analysis and second-order modelling

• DOI: 10.1017/jfm.2023.950
• Publication Date: 2024-03-01T14:01:43Z
• Authors: Christine Lynggår...; Henrik Bredmose; Maude Vincent; Stefan Emil Steff...; Antonio Pegalajar...; Bjarne Jensen; Martin Dixen
• Keywords: Surface gravity waves; 0103 physical sciences; Wave-structure interactions; 01 natural sciences

The dynamics and nonlinear wave forcing of a flexible floating structure are investigated experimentally numerically. floater was designed to match sub-harmonic rigid-body natural frequencies typical wind turbine substructures, with the addition bending mode. Experiments were carried out for three sea states phase-shifted input signals allow harmonic separation measured response. We find weakest that motion is driven by even-harmonic difference frequency forcing, linear strongest state. mode tested in soft, linearly forced layout, stiff second-, third- fourth-harmonic content, increasing severity Further insight gained analysis amplitude scaling resonant A new simplified approach proposed compared recent method Orszaghova et al. ( J. Fluid Mech. , vol. 929, 2021, A32). surge pitch motions dominated potential-flow odd-harmonic response mainly drag pitch. responses reproduced numerically second-order quadratic loads, using computationally efficient calculation method, extended here heave, motions. able reproduce statistics power spectra measurements, including subharmonic heave modes Deeper reveals inaccuracies content can be compensated loads.