Coupled Dynamic Modeling of a Moored Floating Platform With Risers

A time domain coupled analysis capability has been developed to model the dynamic responses of an integrated floating system incorporating the interactions between vessel, moorings and risers in a marine environment. Hydrodynamic responses of the vessel allowing diffraction, radiation damping and wave drift forces on panelized bodies in addition to loads on Morison members, are modeled using the well-established program, MLTSIM. RodDyn, a finite element rod dynamics program, based on Garrett’s rod theory, is an efficient program to model the nonlinear dynamics of risers and moorings. The coupled MLTSIM-RodDyn suite integrates the nonlinear motions and structural analysis capabilities of RodDyn with the extensive hydrodynamic simulation capabilities of MLTSIM. With the fully-coupled dynamic analysis, the integrated system can be analyzed consistently. That is, the forces and moments applied by the rods to the platform are concurrent with the motions imposed on the rods by the platform at their multiple contact points. An asynchronous coupling of these two programs has been developed which allows for a fast simulation of this very complex problem. A worked example showing the nonlinear coupled analysis, is elaborated with systematical comparison with uncoupled analysis.