ABSTRACT

The review of research on the hydroelasticity shows that understanding of the subject has been increased but discussions of practical implications of hydroelasticity to ship design are rare. The authors aimed to change this and investigated how allowance for the hydroelasticity affects assessment of ship performance. This has been illustrated by analyzing a modern cruiseship in the aftship slamming condition with and without hydroelastic interaction. The scope of work included analysis of a simplified hydroelastic model, which reproduces important structural ship properties such as whipping and local aftship vibration modes. The hydroelastic interaction has been modeled at the slamming position only. The following ship design criteria have been considered: passengers discomfort, overall hull girder strength and local strength. The analysis has been described to facilitate the reader with a possibility to carry out a similar analysis of his design.

INTRODUCTION

First a clear definition of the term hydroelasticity will be given. The hydroelasticity can be defined in a very simple way. The hydroelasticity is a fluid-structure interaction. This means that the system includes two parts: the water/air domain and the structure. During the impact the water pressure acts on the structure and the structure deforms. At the same time the speed of the structural deformation influences the pressure in the water. This interaction is shown in Fig. 1. If no hydroelasticity is present (Fig. 2) the problem is solved in the traditional two steps approach. First, the hydrodynamic loads are defined assuming that the structure penetrating the water is rigid. In this paper a structure of a typical modern cruise liner is analyzed in order to investigate the role of hydroelasticity in practical assessment of ship performance. Aftship slamming has been chosen as a case study, because several modern cruise liners are prone to it (Fig. 3).

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