It is critical to be able to estimate a ship׳s response to waves, since the resulting added resistance and loss of speed may cause delays or course alterations, with consequent financial repercussions. Slow steaming has recently become a popular approach for commercial vessels, as a way of reducing fuel consumption, and therefore operating costs, in the current economic and regulatory climate. Traditional methods for the study of ship motions are based on potential flow theory and cannot incorporate viscous effects. Fortunately, unsteady Reynolds-Averaged Navier–Stokes computations are capable of incorporating both viscous and rotational effects in the flow and free surface waves. The key objective of this study is to perform a fully nonlinear unsteady RANS simulation to predict the ship motions and added resistance of a full scale KRISO Container Ship model, and to estimate the increase in effective power and fuel consumption due to its operation in waves. The analyses are performed at design and slow steaming speeds, covering a range of regular head waves, using a commercial RANS solver. The results are validated against available experimental data and are found to be in good agreement with the experiments. Also, the results are compared to those from potential theory
Hydrodynamic interaction continues to be a major contributory factor in marine casualties and hazardous incidents, in particular in the case of overtaking operations. The situation becomes even worse when the overtaking operation occurs in shallow and narrow channels where the interaction can cause the vessels to collide and, in one case has caused the capsizal of the smaller vessel with loss of life. The aim of this paper is to propose a methodology, as well as to discuss the development of a numerical program, to predict the ship-to-ship interaction during overtaking operations in shallow water.Since the vessels involved in the present study have different forward speeds, an uncoupled method will be used to solve the boundary value problem. The in-house multi-body hydrodynamic interaction program MHydro, which is based on the 3D Rankine source method, will be used and extended here to investigate the interactive forces and wave patterns between two ships during an overtaking operation.The present calculations are compared with model test results as well as published CFD calculations.Very satisfactory agreement has been obtained, which indicates that the proposed methodology and developed program are successfully validated to predict the hydrodynamic interaction between two ships advancing in confined waters. The discussions also highlight the speed effects.
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