Fast computation for vibration study of partially submerged structures using low resolution hydrodynamic model

A fast computation scheme is presented for simulating fluid–structure interaction of partially submerged structures. Fluid added mass is simulated using the boundary element method, which only requires a mesh at the fluid–structure interface while satisfying the far field boundary conditions in a semi-infinite domain. The boundary element solver is coupled to a finite element solver for structural vibration analysis. To speed up the boundary element simulation, a low resolution and geometrically simplified surface mesh was used. A projection scheme is introduced to map fluid elements to structural elements, allowing proper transfer of displacement and fluid loading between the two solvers. A series of low-resolution meshes for a realistic container ship model were used to study the efficiency of the proposed scheme, comparing the errors incurred in calculating the wet natural frequencies against the speed-up in computation. With a 20 times decrease in the number of boundary elements, the relative error in wet natural frequency calculation was found to be less than 10%, while computation speed-up was found to be almost 500 folds.