Recently LNG FPSO is one of hot issues in offshore floating body dynamics, which requires accurate analysis of hydrodynamic interactions between two vessels; LNG FPSO and shuttle tanker. In many cases of conventional tandem mooring of FPSO and shuttle tanker, hydrodynamic interaction between FPSO and shuttle tanker was ignored under the assumption that the interactions are not so large to be accounted for. Such assumption implicitly presumed that ignorance of the hydrodynamic interaction gives conservative estimates of behaviors of both ships-FPSO and shuttle tanker. This paper aims to experimentally investigate basic interaction characteristics of tandem moored vessels and side-by-side moored vessels. Model tests were carried out for tandem moored tankers and side-by-side moored tankers in regular waves. Motion responses and drift forces of two vessels were measured and change of drift forces is mainly investigated. Interaction characteristics will also be investigated for change of distances between two vessels as well as types of mooring pattern; tandem and side-by-side moorings. All the cases of two-body interactions was compared with calculations using a higherorder boundary element method based on generalized multi-body interaction theory(Choi and Hong, 2001).
Mooring pattern of conventional FPSO and shuttle tanker has been a tandem type in which offloading operation was carried out in such a way that shuttle tanker located sheltered region behind FPSO and distance between them is about l/4 to l/3 of ship length. While a new side-by-side mooring has been paid attention because of appearance of LNG FPSO-shuttle tanker system in which offloading operation is carried out under parallel position and distance between them is very close. In such a case of side-by-side mooring with very close distance between them, hydrodynamic interaction between FPSO and shuttle tanker becomes very important in operation as well as in design of mooring system.
