Numerical Simulation of Small Scale Moored Vessel Motions with Dynamic Mooring Lines

Abstract

Small scale Liquefied Natural Gas (LNG) has been proven as an effective solution to make the natural gas available for the archipelagic area. The small scale LNG is suitable to meet the demand of LNG power plant development at the archipelagic area of Indonesia. Subsequently, small scale moored vessels are needed to support the LNG distributions. To ensure the safety and reliability of the small scale moored vessels, motion analysis of a moored vessel including mooring line motions should be conducted. This motion analysis will become important because of the environmental conditions that tend to be more extreme and deeper water depth comparing with the other parts of Indonesia. It will be a challenge to design the moored vessels operated in the circumstances. Furthermore, accurate estimation of mooring line tension is needed to evaluate the reliability of the mooring lines. The dynamic effects of mooring lines which are often neglected in general mooring analysis methods must be considered. Moreover, the motion analysis solving the moored vessel motion and mooring lines simultaneously should be introduced to consider the interaction between them. In this paper, numerical simulations are conducted to investigate the small scale moored vessel motions in the archipelagic area of Indonesia considering the dynamic effects of mooring lines. Three-dimensional lumped mass method is used to calculate the dynamics of mooring lines while the Manoeuvring Modeling Group model is used to estimate the vessel motions in the horizontal plane. The calculated vessel motions are later on combined with the mooring line motions to introduce the coupledmotion effects between vessel and lines. Finally, the environmental data representing the considered area is adopted to characterize the external forces acting on the vessel. The results indicate that the moored vessel motions reflect the effects of dynamic mooring lines associated with the environmental conditions of the considered area. Maritime Safety International Conference (MASTIC 2018) Published by CSP © 2019 the Authors 127