Hydrodynamic Response of Floating Coupled Spar in Deep Sea

Abstract

Various advanced floating structures were proposed and developed till date due to their cost effectiveness and productiveness in deep and ultra-deep water exploration. Spar has been seen as a latest and productive alternative amongst the all type of floating offshore platform. However, the precise behavior of fully coupled action of the platform in deeper water is still a great issue to be forecasted in actual sea environment. Dynamic analysis for fully coupled 3D model of floating spar platform structure can be a resourceful tool to predict the responses, where primary assemblage of Spar platform and mooring lines are considered in a joined compact coupled system. To define accurately the interaction between the Spar and mooring lines, coupled dynamic analyses are appropriate to get responses in deep sea. Considering the coupling effect of the platform and its mooring system, hydrodynamic analyses of a coupled Spar has been carried out in time domain. Also, Response Amplitude Operator (RAO) has been studied of every motion and mooring tension with Fast Fourier Transform method (FFT). The numerical simulation and motion investigations are completed with the commercial finite element (FE) package ABAQUS/AQUA. The purpose of this paper is to investigate the response of fully coupled Spar platform under regular ocean environment. Tension to the deformable mooring lines is equally distributed. Wave loading acts simultaneously on the rigid spar hull and deformable mooring line. Rigid body resonant motions influence the dynamic motion responses of Spar. Damping of the mooring line in coupled Spar-mooring system decreases the top tension of its mooring system after certain wave duration. The wave induced effects have been evaluated and discussed to investigate their interaction with the floating spar platform. RAO of the motion responses and mooring tension are consistence to predict motion of the Spar platform. It shows energy concentrate peaks of the floater's response with the frequency.