A numerical investigation of the flexible vertical response of an ultra large containership in high seas compared with experiments

• The vertical response of an Ultra Large Containership in high seas is analysed and compared with experiments.
• The experiment was conducted on a free running model with aluminium back bone with flexible response measured.
• The ship was tested in regular waves to analyse springing, and in severe irregular seas for whipping response.
• The hydroelastic response of the ship is numerically calculated using a body nonlinear time domain method.
• The numerical vertical bending moments are reasonably in good agreement with the experimental results.

The vertical response of an Ultra Large Containership in high seas is analysed by means of numerical methods, which are compared with experiments. The experiment was conducted in a wave tank on a free running model with aluminium back bone and the flexible response of the ship is measured. The ship was tested in regular waves of moderate amplitude to analyse springing, and in severe irregular seas for whipping response. It was found that the flexibility of the model increases the largest sagging peak by up to 32%. The hydroelastic response of the ship is numerically calculated using a body nonlinear time domain method based on strip theory. A practical engineering method is followed for calculating the dependency of the hydrodynamic forces on the geometrical nonlinearity of the wetted hull. The time domain code is coupled with a Finite Element Model and the ship hull is modelled as a non-uniform Timoshenko beam. The ship responses in moderate seas are very well calculated by the numerical method. Even though vertical motions in very high seas are slightly overestimated by the numerical results, the numerical vertical bending moments are reasonably in good agreement with the experimental results.