Nonlinear Lid Technique: Application to Gap and Moonpool Resonance

This paper focuses on the implementation of a nonlinear Lid Technique, as done in the software Diodore™. Several dummy plates are used and modelled as mechanical structures with their own degrees of freedom, capable to account for nonlinear damping. The paper describes first the general equations governing the multi-body sea-keeping model including dummy plate structures, and the expression of the relative quadratic damping. In a second step, examples of applications with gap and moonpool are exposed, demonstrating the capability of the nonlinear Lid Technique with multiple plates to render not only the piston mode, but also the other modes of deformation of the free surface.

On the Handling of Moonpool Resonances by Green’s Function Methods

In this paper, we will investigate the numerical treatment of irregular frequencies and moonpool resonance by using a Green’s function method. We will look at the interaction of these two resonances and how much the moonpool resonance will influence other results. We will also look at the importance of the meshing including the addition of a mesh in the moonpool. Such a mesh is normally only used when we want to include damping of the moonpool resonance, but it will be shown that including this mesh may be beneficial also without damping. In addition to the wave elevation in the moonpool we will also investigate the effect of the moonpool resonance on the motions, sectional loads and mean drift forces.