A discrete-modules-based frequency domain hydroelasticity method for floating structures in inhomogeneous sea conditions

Abstract

Based on the three-dimensional (3D) potential theory and finite element method (FEM), this paper proposes a new numerical method for hydroelastic predictions of floating structures in inhomogeneous seabed and wave field conditions. The continuous floating structure is first discretized into rigid modules connected by elastic beams. The motion equations of the entire floating structure are established according to the six degrees of freedom (6DOF) motions of each module by coupling the hydrodynamics of the modules with the structural stiffness matrix of the elastic beams in the frequency domain. By applying different wave excitation forces onto different modules, this discrete-modules-based method then uniquely realizes application of various wave excitation forces onto different modules of the structures in inhomogeneous waves. The hydroelastic responses of a plate and a Wigley hull under an even and uneven seabed using the proposed method are verified against the results from the published model tests and the conventional 3D hydroelastic method. Finally, the effects of inhomogeneous waves on the distributions of the bending moment, shear force and vertical displacements of the freely floating plate are investigated. The results show that the inhomogeneity of waves may induce about 2~3 times increase of the force responses in a specific wave frequency.

Experimental Data of a Floating Cylinder in a Wave Tank: Comparison Solid and Water Ballast

“…The presented experimental set-up uses a floating structure to investigate interaction between the the inner and outer water body (fluid-structure-fluid interaction). Similar studies for very large floating structures are available in the literature [6][7][8][9], but are typically limited to small motions. Ships containing liquefied natural gas are another comparable application.…”

Comparison of a Floating Cylinder with Solid and Water Ballast

“…The correct prediction of the motion and forces acting on a floating body are essential for the structural and mooring designs [10,11]. The response of Very Large Floating Structures (VLFS) [12][13][14], including the inner water level [15], have only been investigated for small motions. A wide range of studies investigate sloshing inside various containments and mainly focus on the resultant peak wall pressure [16][17][18], as well as being used for validation experiments [19][20][21].…”

Hydro-Elastic Analysis of a Floating Bridge in Waves Considering the Effect of the Hydrodynamic Coupling and the Shore Sides

“…Stiffness matrix of each element in local coordinate system can be obtained based on Young's module and cross-sectional properties. The stiffness matrix in the local coordinate system can be transformed to the global coordinate system based on small deformation assumption, [13] In the structure analysis, structural damping is simplified using the Rayleigh damping model, so motion equation in the global coordinate system can be defined as:…”

“…From the view of hydroelasticity, the deformation of the structures might be considered using a mode-superposition method. A new method for the hydroelastic responses of flexible floating structures in waves, which is so called "Discrete Modules Based" method has been recently proposed by Wei et al [13] where, a VLFS will be divided into sub-modules connected by series elastic beams, and each submodule is regarded as a rigid body. Under this circumstance, the motions of each module are affected by the hydrodynamic interactions with the surrounding modules and are restricted by the displacement continuity of adjacent modules.…”