Coupled analysis between mooring system and VLFS with an effect of elastic deflection of floater

Abstract

The conventional mooring analysis considers the motion of the floater as a rigid body. However, as the dimension of the floater increases, the elastic deflection of the floater may become significant which can have an impact on mooring tensions. In this paper, based on the three dimensional hydroelasticity and quasi-static mooring analysis method, a coupled numerical analysis method for a Very Large Floating Structure (VLFS) and mooring system is established. The elastic deflection amplitudes and phases of various modes of a VLFS are first computed in regular waves in frequency domain, these are then converted into time series for the specified real sea state, and time domain simulations for the vessel's motion and mooring tension are performed. In the time domain simulation, the displacements at mooring connection points on the vessel include both the rigid motion and elastic deflection of the vessel. A single VLFS module was analyzed together with a mooring system to demonstrate the procedure of the analysis. Furthermore a VLFS consists of three modules with a mooring system was also analyzed. The calculation results match well with the data from model test, which indicates the validity of the numerical method proposed and the computing program developed.