Abstract

To improve the accuracy of the numerical procedure in hydroelastic analysis, two areas are studied in this work. One is the interface methods used to couple the fluid and the structural meshes. The other is the hydrostatic stiffness for use in hydroelastic analysis of flexible floating structures.

Nonlinear, time-domain hydroelastic analysis of flexible offshore structures requires that the structural motion be transferred to the fluid model and the resulting fluid pressure at the fluid-structure interface be transferred from the fluid model to the structure. When the structural mesh and the fluid mesh describe two distinct three-dimensional surfaces, the transfer of the displacement and pressure is both difficult and non-unique. A new transfer methodology based on the variational-based smoothing element analysis (SEA) technique is presented. The displacement transfer uses the original formulation of the SEA, although the application of the procedure to displacement transfer is new. For energy conservation during the reverse pressure transfer, SEA is modified. The transfer method is tested by examining the performance of three floating rigid bodies. Application of the methodology to flexible bodies is also presented. The numerical results show that the method works very well.

The formulation of the hydrostatic stiffness for linear rigid body hydrodynamics is well-known. An explicit formulation for an analogous hydrostatic stiffness in linear hydroelasticity, which is applicable to both rigid body and flexible displacement, is not well-known. Three such formulations have been proposed previously in the literature, none of which is quite correct. An explicit formulation for the complete hydrostatic stiffness matrix for flexible structures, for use in linear hydroelastic analysis, is derived based on a consistent linearization of the generalized external and internal forces. The symmetry of the present formulation for a floating structure is proven analytically, and the unsymmetry of the hydrostatic stiffness for individual finite elements is discussed.