In this study, a series of model tests was performed and the effect of the heading control on the offloading operability of side-by-side moored vessels in multidirectional environments was investigated. During the tests, hawser tensions, fender loads, and relative motions between two vessels were focused, which are the key factors defining the offloading operability. Basically, the heading control is designed to maintain the FLNG (LNG FPSO)’s heading at between wind wave and swell. In the model tests, several heading angles were selected to investigate the impact of the heading control on the offloading operability, which includes the heading angles aligned with swell and between swell and wind wave. The loading conditions of the FLNG and LNGC were chosen to have a similar roll natural period, and the period of swell was also selected close to the roll natural period, which realizes an worst situation.
The model tests proved that heading control improves the offloading operability in the multi-directional environments. However, in the test, as vessel’s heading angle approaches to the direction of swell, the LNGC is exposed to wind wave as much as to increase the relative motion between the two vessels and deteriorate the offloading operability. In the model test campaign, the motion RAOs and horizontal drift forces/moment due to waves for the side-by-side moored vessels were measured and compared with the analytical calculations, which show the strong shielding effect on the wind wave by the FLNG.