The Shuttle tool for the sim- ulation of complex, offloading operations is now capable of side-by-side offloading and offloading from a jetty or
Gravity Based Structure (GBS). This tool should provide vital help for the gas industry as the import of LNG is one of the most important developments for the use of side-by-side offloading.
In 2005, the Joint Industry Project “Offload- ing Operability” was completed and this led to the development and validation of Shuttle. This tool can be used to evaluate the design and operation, to determine the limiting weather criteria and to assess the safety of offshore tandem offloading opera- tions. Within the second, ongoing phase of the project, Shuttle was extended to simu- late side-by-side offloading operations. The calculation kernel of the program was adapted to include fenders between the vessels and the database was extended with wind and current coefficients for strongly shielded vessels.
Wave motions between vessels need to be described in a realistic way as these influ- ence the relative ship motions and mooring line tensions. Most widely-used diffraction analysis tools overestimate the amplification of the waves in the gap, resulting in unstable simulation. A rigid lid applied to the free surface between the two vessels proposed by Huijsmans et al. (2001) overcomes this
problem but provides too much suppression of the waves, resulting in an underestimate of the downtime.
In 2005, Chen formulated a different bound- ary condition for this area between the ships, allowing reduction of the non-realistic wave motions with a damping parameter. This method is now included in the Shuttle tool and damping parameters were tuned against model tests. After tuning of the model parameters against decay tests and wave measurements in the gap, a good comparison was found for the line loads and fender loads in real sea conditions.
Shuttle was developed in close cooperation with the JIP participants, Bluewater, Samsung, BP, Bureau Veritas, Chevron, Sofec, SBM, ExxonMobil, Woodside, Hoegh, Shell, Fendercare, Total, MossMaritime, BHP and MARIN. These companies receive the updated tool, which is only available by joining the JIP and can use it for their own studies or advice to others.
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