Abstract
The seakeeping behaviour of a vessel in shallow water differs significantly from its behaviour in deep water. In shallow water, a vessel's motion responses to incident waves will be affected by hydrodynamic effects caused by the presence of a finite depth. Given that a vessel will sail in shallow water at various times during its service life, such as when entering harbours, it is important to have an understanding of the influence of shallow water on ship motions. In this study, using a commercial unsteady Reynolds–Averaged Navier–Stokes solver, a numerical study of ship motions in shallow water was carried out. Firstly, the characteristics of shallow water waves were investigated by conducting a series of simulations. Then, a full-scale large tanker model was used as a case study to predict its heave and pitch responses to head waves at various water depths, covering a range of wave frequencies at zero speed. The motion results obtained were validated against related experimental studies available in the literature, and were also compared to those from 3-D potential theory. The results were found to be in good agreement with the experimental data. Finally, it was shown that vertical motions were significantly affected by shallow water.
Highlights
Over the last decade, an increasing number of large ships, such as Very Large Crude Carriers (VLCC) have called for a need to understand the performance and behaviour of such ships in shallow water
Only the first term of the series will be retained, assuming that the solutions lie in the asymptotic range
Roache's grid convergence index (GCI) is recommended for use by both the American Society of Mechanical Engineers (ASME) (Celik et al, 2008) and the American Institute of Aeronautics and Astronautics (AIAA) (Cosner et al, 2006)
Summary
An increasing number of large ships, such as Very Large Crude Carriers (VLCC) have called for a need to understand the performance and behaviour of such ships in shallow water. Even some open sea areas (for instance some areas in the North Sea) can be regarded as shallow water These large vessels are loaded and unloaded in exposed areas, where they are moored or secured to buoys or jetties. These designated terminals are located as close to shore as possible, mostly in shallow water. 15,730,897 12,451,124 8,909,383 calculations suggest that the iterative errors for the heave and pitch transfer functions were 0.200% and 0.195% of the solution for the finest grid-spacing and smallest time-step, respectively. The convergence studies were performed with triple solutions using systematically refined grid-spacing or time-steps.
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