ABSTRACT

Two typical close proximity situations are side-by-side mooring and Gravity Based Structure mooring. In these situations strong interaction effects play a significant role in the prediction of the motions and the mooring loads. Interaction does not only have an effect on wave forces, added mass and damping, but also on the drift forces. Further the viscous damping of the motions of the vessel in close proximity of another structure and moored in shallow water is a complex issue. Finally there is a significant interaction effect in the wind and current forces. A numerical time domain simulation model has been developed for the prediction of the hydrodynamic response of structures moored in close proximity. The model has been validated by comparing simulation results with model test results. It was found that for an accurate prediction of the vessel motions the following factors play a significant role: - A full hydrodynamic interaction matrix should be used in time domain simulations - accurate input for the viscous damping model - application combined linear and quadratic damping model.

INTRODUCTION

In a lot of situations floating structures are moored in close proximity of other structures, see Figure 1: - during side-by-side mooring along a moored or sailing vessel (lightering) - in the case of mooring along a Gravity Based Structure (GBS) - when a vessel is moored along a quay in a harbor The related hydrodynamics are complex: this relates to the multi-body interaction in the wave forces, added mass and damping, but also to the drift forces. Further the viscous damping of the surge, sway, yaw and roll motion of the vessel in close proximity of another structure is a complex issue. The small distances between the sides of the structures results in large velocities of the flow around the bilges.

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