This paper considers the analysis of ship springing using WISH-FLEX which has been developed at Seoul National University for hull-girder hydroelasticity in waves. WISH-FLEX is based on a hybrid BEM-FEM method to couple the boundary value problems of two distinct domains: fluid and structure. A strong-coupling scheme is applied to solve fluid-structure interaction by using a fixed-point iteration scheme. This study focuses particularly on the observation of computational results for the different beam modeling of ship structure and different structural damping. Even though the same computer code is applied, the computational results can be dependent on user and the modeling of computational parameters such as grids, beam modeling, and external forces. The ship model considered in this study is a 10,000 TEU containership which has been experimented at MOERI/KORDI as WILS II project. The computed motion RAOs and the time-histories of load signal are compared with experimental data, and the agreement and discrepancy are described. This kind of observation may help us to understand the uncertainty level of numerical analysis in ship springing analysis.
Hydroelastic hull-girder vibrations referred to as springing and whipping have come to real engineering issues with recent strong demands for larger and faster ships than ever. As ship size is getting larger, the occurrence probabilities of springing and whipping are getting higher in general, and consequently more potential of fatigue damage can be easily predicted. The primary mechanisms of springing and whipping are basically the same, but the excitation characteristics are very different. Springing is excited by ocean waves, while whipping is the transient response of hull-structure due to impulsive slamming force. This study focuses on ship springing. However, the recent trend of building very large containerships makes springing as one of significant sources of global ship vibration.