A hydroelasticity method for vibrating structures containing and/or submerged in flowing fluid

This paper presents a method for investigating the dynamics of elastic structures containing and/or submerged in flowing fluid. The method presented is based on a boundary integral equation method in conjunction with the method of images, in order to impose appropriate boundary condition on the fluid's free surface. The method of analysis can be applied to any shape of cylindrical structure partially in contact with flowing fluid. In the analysis of the linear fluid-structure system, it is assumed that the fluid is ideal, i.e., inviscid, incompressible and its motion is irrotational. It is assumed that the flexible structure vibrates in its in vacuo eigenmodes when it is in contact with flowing fluid, and that each mode gives rise to a corresponding surface pressure distribution on the wetted surface of the structure. The in vacuo dynamic properties of the dry structure are obtained by using a standard finite element software. In the wet part of the analysis, the wetted surface is idealized by using appropriate boundary elements, referred to as hydrodynamic panels. The fluid-structure interaction effects are calculated in terms of the generalized added mass coefficients, generalized Coriolis fluid force coefficients and generalized centrifugal fluid force coefficients. In order to demonstrate the applicability of the proposed method, a circular cylindrical shell, simply supported at both ends, was adopted for the calculations. The cylindrical shell was considered separately with rigid and flexible extensions at its ends. To assess the influence of flowing fluid on the dynamic behavior of the shell structure, the non-dimensional eigenfrequencies and associated eigenmodes are presented as a function of the non-dimensional fluid velocity. The predictions compare well with available analytical calculations found in the literature.