Numerical study on deployment of subsea template using coupled and uncoupled model

Abstract

This study compares deployment of a subsea template simulated as a coupled model and as an uncoupled model in the time domain simulation software Orcaflex. Defining vessel motion as prescribed simplifies the model and will therefore also decrease the simulation time. Models with predefined vessel motions are called uncoupled models. Vessel motion in a coupled model is a continuously calculated reaction to the forces acting on the vessel. Some software might struggle to run coupled models. The deployment simulations are narrowed down to focus on the incident where the template crosses the splash zone when lifted with an offshore construction vessel. Noticeable differences between the allowable sea state results are observed from the two different simulation methods. Running the time domain simulation as an uncoupled model gives lower allowable sea states than the results from the coupled time domain simulation model.