Abstract
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.
Highlights
Understanding the behaviour of a vessel in a real seaway is critical for determining its performance
It was shown that the total resistance coefficient in calm water at service speed is underpredicted by 4.95% compared to the related towing tank results
For the simulations in the presence of waves, a numerical wave probe was inserted between the inlet and the ship to measure the generated waves
Summary
Understanding the behaviour of a vessel in a real seaway is critical for determining its performance. Beck and Reed (2001) estimate that in the early 2000s, 80% of all seakeeping computations at forward speeds were performed using strip theory, owing to its fast solutions. As discussed by Newman (1978), the conventional strip theories are subject to some deficiencies in long incident waves and at high Froude numbers This is thought to be caused by the evolution of forward speed effects and the complex nature of the diffraction problem. When generating the mesh for the simulations in calm water, the refined mesh area for the free surface was kept relatively small, compared to that used in the seakeeping simulations In this case, based on prior experience, a minimum cell size of 0.0785% of LBP in the vertical direction was used to capture the flow features in the free surface.
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