A coupled frequency and time domain approach for hydroelastic analysis of very large floating structures under focused wave groups

This paper presents a Python-based scheme for simulating the hydroelastic response of very large floating structures (VLFS) under extreme conditions which are represented by focused wave groups. Applying the modal expansion method, we decouple the fluid-structure problem into a hydrodynamic problem in terms of velocity potentials for the fluid and a mechanical problem for the structure. The hydrodynamic problem is solved by the higher-order boundary element method in the frequency domain, while the structural analysis is performed by a time-domain finite element model. In order to validate the proposed scheme, numerical simulations are carried out on a scaled model of VLFS in regular and random waves. Both analytical and discrete numerical modal shape functions are used for representing the elastic deformations. The Mindlin plate theory is used for the finite element model. Extensive convergence studies of finite element model meshes, hydrodynamic model meshes and elastic mode numbers are carefully carried out. Good agreements of the vertical displacement, bending moment and shear force amplitudes of the floating plate are found between the predictions of the present model, and experimental data and numerical results in the literature for regular and random waves. The hydroelastic responses of the scaled model in focused wave groups are then investigated. A modified NewWave model is proposed to generate focused pressure in linear wave groups, and the results show the effectiveness of the proposed model. Influence of the focal position, water depth, incident wave angle, and peak spectrum frequency and bandwidth of the focused wave groups on the hydroelastic response of the plate is also studied. The proposed approach is shown promising for hydroelastic analysis for more complex VLFS in realistic sea states.