Coupled Dynamic Modelling of Moored Floating Structure

Abstract

This paper is aimed to explore the effects of the wave directions and mooring lines on the dynamic characteristics of the semi-submersible offshore platform. The coupled numerical analysis is generated between the platform motions, the mooring lines and the marine environment. Four column semi-submersible platform serves as a floating body, four mooring lines and the wave environment constitutes the numerical model. Wire elements with different slack-taught types are utilized in modelling the mooring lines. On the other hand, the platform is considered as a rigid body having six degrees of freedom (6 DOF) motions. Several wave incidence directions are used to symbolize the marine environment. Besides, tensions of the mooring lines as well as the motions of the platform that changes by time are determined according to different configurations of the mooring lines and directions of the waves. Bidirectional fluid structure interaction analysis is performed to obtain the most critical results among the configurations and the directions. Fully nonlinear free surface simulation is carried out due to the Coupled Eulerian Lagrangian (CEL) analysis that is generated by the finite elements method and the results are compared with the results determined from analytic solution of free surface elevations.