Coupled Dynamic Analysis of a Moored Spar Platform in Time Domain

Abstract

A time-domain simulation method is developed for the coupled dynamic analysis of a spar platform with mooring lines. For the hydrodynamic loads, a time domain second order method is developed. In this approach, Taylor series expansions are applied to the body surface boundary condition and the free surface boundary condition, and Stokes perturbation procedure is then used to establish corresponding boundary value problems with time-independent boundaries. A higher order boundary element method is developed to calculate the velocity potential of the resulting flow field at each time step. The free-surface boundary condition is satisfied to the second order by 4th order Adams-Bashforth-Moultn method. An artificial damping layer is adopted on the free surface to avoid the wave reflection. For the mooring-line dynamics, a geometrically nonlinear finite element method using isoparametric cable element based on the total Lagrangian formulation is developed. In the coupled dynamic analysis, the motion equation for the hull and dynamic equations for mooring lines are solved simultaneously using Newmark method. Numerical results including motions and tensions in the mooring lines are presented.

Dynamic Responses Coupled Analysis of Fpso in South China Sea

“…The equilibrium equation of slender rod section can be provided by Newton's second law and moment equilibrium conditions. Combine the equations (12) and 13can obtain the equation as follows:…”

“…Fine and Grue [9] obtain the damping of low frequency yaw by solve the radiation/diffraction problem with low speed. Yang and Teng [10][11][12] developed a full time domain analysis method to calculate the wave force and the result accurately to second-order. Recently, there are three models were used to simulate mooring line, such as the lumped mass model, the catenary model and slender rod model.…”