Analysis of Hydroelasticity of Floating Shiplike Structure in Time Domain Using a Fully Coupled Hybrid BEM-FEM

A fully coupled time-domain ship hydroelasticity problem focusing on a springing phenomenon is considered in this study using a hybrid boundary element method (BEM) finite element method (FEM) scheme. The fluid domain surrounding a flexible vessel is handled with a boundary element method adopting a higher-order B-spline Rankine panel method. The structural domain is modeled by a finite element method relying on the one-dimensional beam element, which is able to capture the coupling effect between torsion and bending as well as warping distortion. Coupling between the two subdomains is realized by the Newton method in which an exact Jacobian matrix is derived by solving both fluid and structure tangent problems. The calculation is repeated until the solution reaches convergence. Thanks to the positive aspects of this implicit scheme, numerical instability related to the time integration can be avoided without relying on infinite frequency added mass, which is inevitable when an explicit scheme is used. Moreover, a direct integration scheme, such as the Newmark-beta method, for structural problems can be used, and this formulation can be easily extended to the case with structural nonlinear effect, such as large deformation. The developed computer program is validated through comparison with published experimental data, ending up with good correspondence between the two results. Validation is also achieved through a comparative study on rigid body motion with an existing six degrees of freedom (6-DOF) ship motion program.