Consistent Hydro-Structure Interface for Evaluation of Global Structural Responses in Linear Seakeeping

The difficulties related to the equilibration of the 3D FEM structural model, in the context of hydro-structure interactions in linear seakeeping are discussed. Different philosophies in modeling the structural and hydrodynamic parts of the problem, usually lead to very different meshes (hydro and structure) which results in unbalanced structural model and consequently in doubtful results for structural responses. The procedure usually employed consists in using different kinds of interpolation schemes to transfer the total hydrodynamic pressure from hydrodynamic panels to the centroids of the structural finite elements. This approach is both, very complex for complicated geometries, but also rather inaccurate. The method that we propose here is based on two main ideas: 1. Pressure recalculation instead of interpolation; 2. Separate transfer of different pressure components (incident, diffraction, radiation & hydrostatic variation). The first point removes the difficulties related to the interpolation techniques, and allows for a very robust method of pressure transfer. The second point ensures the perfect equilibrium because the body motions are calculated after integration over the structural mesh, which means that the equilibrium is implicitly imposed. It should be noted that this procedure is not completely straightforward and several numerical “tricks” need to be introduced. However, once these difficulties are solved, the final numerical code is extremely robust and can be easily coupled with any of the general 3D FEM packages.Copyright © 2008 by ASME