During offshore installation and underway replenishment, two vessels are side by side arranged in close proximity. A time domain high order Rankine panel method is developed and applied to analyze hydrodynamic interactions of side by side vessels in waves in the present paper. Radiation and diffraction problems are solved with linearity theorem. And for forward speed problem, both double body (DB) flow and uniform stream (US) linearized computations are carried out. Added mass, damping coefficients, hydrodynamic forces and motions responses of side by side vessels are computed and hydrodynamic interactions are investigated.
Numerical programs are developed and used to calculate hydrodynamic coefficients and forces of side by side arranged modified Wigley hull and a rectangular barge of zero speed. Present results agree well with model test data and resonance phenomenon are obtained by computation. Further numerical investigation is carried out for a Supply ship and a Frigate advancing in waves parallel in close proximity. Ship motions of DB linearization computation are in generally better agreement with experiments than of US linearization method. Results of motions response of smaller Frigate in condition of two ships on parallel course are quite different with that of single ship condition due to the existence of bigger Supply ship. In addition, results show two ships with forward speed would undertake attracting lateral force. Detailed discussions on numerical results are carried out.
Study on hydrodynamic interactions of side by side vessels in close proximity in waves is of great importance. The corresponding situations include offshore installation, LNG-FPSO system, and underway replenishment of ships advancing in waves. In these cases, hydrodynamic forces and vessels' motions response would be quite different in comparison to single body condition and should be carefully studied.
Potential flow theory is favorable in ship hydrodynamic analysis due to its practicability. Original work was carried out by Korvin- Froukovsky(1955), Silverstein (1957), Hess and smith (1964) and other researches. After that, many have studied on ship seakeeping prediction. Among those, Tasai (1967), Ogilvie and Tuck (1969), Salvesen et al. (1970) came up with new strip theory, rational strip theory and STF method, respectively in early years. Strip theory is restricted by low speed and high frequency assumption and ship shall be slender, so it cannot be widely used in marine and ocean engineering. Three dimensional potential method that can be applied to ships and floating bodies with arbitrary form was then developed. The method is classified into free surface Green's function method and Rankine source method. The former adopts Green's function that satisfied linearized free surface and radiation condition, so source and diploe are only needed to be distributed on ship hull. Noblesse (1982), Newman (1984), Faltinsen and Michelsen (1974) used the method to solve wave body interactions in frequency domain. Clement (1998), Bingham (1994), Qiu (2013) studied on time domain simulation of ship seakeeping with transient Green's function. Rankine source method employs basic solution 1/r of Laplace equation as Green's function. Dawson (1977) first applied Rankine source method to compute steady ship wave. Nakos (1990) studied on steady and unsteady ship wave problems by quasi-linear formulation with frequency domain Rankine source method respectively. Kring et al. (1996) and Kim et al. (2013) developed a weak-scatterer time domain nonlinear method for forward speed problem.
