Beam-like ship vibration analysis in consideration of fluid-structure interaction

To analyze ship vibration, the corrected added mass is to be calculated, which is derived from two-dimensional fluid added mass based on the strip theory and three-dimensional correction factor in consideration of the shape of ship. In case of newly built large-sized vessels, it is revealed that the results of the beam-like ship vibration analyses using the three-dimensional correction factors proposed by Lewis and Kumai have evaluated inaccurately, because the ratio of width to depth of ship is a larger than those for the existing vessels. Therefore, it is necessary to improve the accuracy of results of vibration analyses of large-sized vessels in contact with fluid. In this paper, a new method is introduced which can calculate the hydrodynamic inertia force of fluid for three-dimensional container ship. It was calculated by using the Boundary Element Method and the concentrated added mass for each strip of ship was evaluated, and then the vibration analysis for the ship was performed. Using this method, three dimensional hydrodynamic force of ship can be obtained for any arbitrary shape of ship. The ship vibration analysis can be performed simply by applying the calculated fluid added mass to beam-like ship. For verification, vibration analysis was performed using the Strip Theory Method and the improved method for ship structure of Open Top Container Ship Model at first. And then, an original Open Top Container Ship was used to analyze by new method, compared with result of present analysis method and measurement data of original ship. The efficiencies of beam-like ship vibration analysis for hull girder modes by improved method were demonstrated.