Application of the finite element method to fluid-structure interaction in ship vibration

The fluid-structure interaction problem in ship vibration is studied. The basic formulation in terms of the dynamic pressure induced by a vibrating structure is given. The finite element method is applied to the solution of the fluid equations. The coupling of the fluid and the structure is formulated using the interface element concept. The coupling matrices for several interface elements are derived in details. The formulation leads to an added-mass matrix, which represents the effect of the fluid in ship vibration. The corresponding coupled eigenproblem is solved using the so-called modal approach, i.e. the dry modes of the structure are used as Ritz functions in the final solution. The details of this solution procedure are given also in the case when the system has rigid body modes. The computer implementation of the developed procedures is described. Several numerical examples are given and some tentative conclusions are drawn on the real fluid effect in beam like vibrations of a ship hull girder. The procedures are applied to a dynamic analysis of a 28 000 tdw bulk carrier and a comparison with experimental results is given.