The main transport channel of the global economy is represented by shipping. Engineers and hull designers are more preoccupied in ensuring fleet safety, the proper operation of the ships, and, more recently, compliance with International Maritime Organization (IMO) regulatory incentives. Considerable efforts have been devoted to in-depth understanding of the hydrodynamics mechanism and prediction of ship behavior in waves. Prediction of seakeeping performances with a certain degree of accuracy is a demanding task for naval architects and researchers. In this paper, a fully numerical approach of the seakeeping performance of a KRISO (Korea Research Institute of Ships and Ocean Engineering, Daejeon, South Korea) container ship (KCS) container vessel is presented. Several hydrodynamic methods have been employed in order to obtain accurate results of ship hydrodynamic response in regular waves. First, an in-house code DYN (Dynamic Ship Analysis, “Dunarea de Jos” University of Galati, Romania), based on linear strip theory (ST) was used. Then, a 3D fully nonlinear time-domain Boundary Element Method (BEM) was implemented, using the commercial code SHIPFLOW (FLOWTECH International AB, Gothenburg, Sweden). Finally, the commercial software NUMECA (NUMECA International, Brussels, Belgium) was used in order to solve the incompressible unsteady Reynolds-averaged Navier–Stokes equation (RANSE) flow at ship motions in head waves. The results obtained using these methods are represented and discussed, in order to establish a methodology for estimating the ship response in regular waves with accurate results and the sensitivity of hydrodynamical models.

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Unfavourable environmental conditions associated with an insufficient stability margin adopted in the design process may determine ship capsizing. One of the most critical situations is generated when the ship moves on longitudinal waves, at parametric resonance condition. In this paper, the theoretical and experimental investigations on transverse stability of a cargo ship on regular longitudinal waves are considered. During the seakeeping model tests on longitudinal waves, the occurrence of induced roll motions were observed and measured. The restoring moment on longitudinal waves was determined based on theoretical and experimental methods. A computer code has been implemented in order to calculate the main parts of the restoring moment i.e. Froude-Krylov, diffraction and radiation components. In order to reproduce the real physical phenomenon, captive and semi-captive model tests were correlated. The radiation and diffraction forces and moments and the restoring moment on regular longitudinal waves were measured. The agreement of the calculated solutions with the experimental results indicates the possibility of using the adopted hydrodynamic model in the design process.

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