Numerical Investigation of Hydroelastic Effects on Floating Structures

Abstract

Hydroelasticity effects of an offshore floating structure comprise the combined motions and deformations of the floating body responding to environmental excitations. The review of research on hydroelasticity of very large floating structure shows that understanding the physical phenomenon has increased, but discussions of practical implications of hydroelasticity on offshore structure design are rare. Conventionally, floating structure designs are based on a rigid quasi-static analysis, meaning that the hydrodynamic loads are estimated under rigid assumption and then applied to the elastic structure regardless of structural inertia. Here, the hydroelastic behavior of a standard floating module designed within the scope of the Space@Sea project was numerically investigated, and the role of hydroelasticity in the practical assessment of a large floating structure was demonstrated. The fluid dynamics relied on a Computational Fluid Dynamics (CFD) code, and the structural responses were computed by a Computational Structural Dynamics (CSD) solver. The CFD-CSD solver was coupled using an implicit two-way coupling approach, computing the nonlinear 6-DoF rigid body motion separately from linear elastic structural deformations. First, the numerical model was validated against benchmark test data, and then a standard floating module in waves was assessed in terms of structural integrity and motions. Maximum stresses and bending moments obtained by the coupled CFD-CSD approach and the traditional rigid-quasi-static approach were compared, and the implication of hydroelasticity on the floating module was assessed. The hydroelastic criterion and the validity of a rigid a quasi-static analysis determined the effects on dynamic responses.