Critical analysis of the finite element approach for structural vibration calculations in cruise ship structures

The numerical analysis of ship structures has been an established practice for decades. However, while static analysis provides reliable results with high accuracy, the dynamic analysis of huge ship structures still presents many limitations. The wavelength of flexural waves propagating into the hull decreases with increasing frequency, requiring a progressive decrease of the mesh used. Using very fine meshes to discretise large commercial ships may lead to an unsolvable problem, even with current computational capabilities. On the other hand, coarse meshes only allow for obtaining consistent results at very low frequencies, where the modes involve global deformations of the hull girder. In this paper, a study aimed at define the mesh dimension required to analyse large cruise ship structural vibrations is performed. Modes, frequency response, and energy propagation paths were analysed to understand the differences between different modelling solutions. The results gave valuable indications on the ship’s dynamic numerical analysis.