engleski

Hydroelastic loading and response of ultra large container ships

The importance of mathematical models for ship hydroelastic analysis grows with the design of ever larger container ships which have specific design and exploitation characteristics. Compared with other merchant ships, they are characterized by relatively lower torsional stiffness, which in combination with encounter sea states related to their higher speed of approximately 27 knots can cause resonance effects. This paper is based on research activities and results of the EU FP7 project Tools for Ultra Large Container Ships (TULCS), with particular emphasis to the part which deals with global hydroelastic loading and response. Special attention is paid to beam structural model based on the advanced beam theory. It includes shear influence on both bending and torsion, contribution of transverse bulkheads to hull stiffness as well as an appropriate modelling procedure of relatively short engine room structure. Along with that, hydrodynamic model is presented in condensed form. Further on, fully consistent formulation of restoring stiffness which plays important role in the hydrostatic model is described. Theoretical contributions are illustrated within the numerical example which includes complete hydroelastic analysis of a 11400 TEU container ship. The validation of advanced beam model is checked by correlation analysis with the vibration response of the fine 3D FEM model. Finally, ship hydroelastic response assessed by sophisticated beam model is compared with the results of fully coupled 3D FEM + 3D BEM hydroelastic analysis. The obtained transfer functions of sectional forces confirm that the developed model is very useful numerical tool for the designer and represents a reasonable choice for determining wave load effects on ULCS, in early design stage.

Container ship; Hydroelasticity; Beam model; Restoring stiffness; Effective stiffness; Modal approach; FEM

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