During the past thirty years, there has been a steady growth in the size and number of ships that use the Strait of Istanbul (Bosporus), which is one of the most difficult, crowded, and potentially dangerous waterways in the world. There have been over two hundred accidents over the past decade resulting in loss of life and serious damage to the environment. Many of the proposed export routes for forthcoming production from the Caspian sea region pass westwards through the Black Sea and the Bosporus en-route to the Mediterranean Sea and world markets. The risks and dangers associated with tanker navigation, maritime accidents and environmental catastrophe are aggravated with the increase in the density of traffic, tanker size and cargo capacity, as well as the nature of the cargo. In order to ease the problem, a Traffic Separation Scheme (TSS) was established and approved by IMO in 1994. This scheme has drastically reduced the number of collisions. However, one-way or two-way suspension of traffic in the Bosporus is inevitable for ships that cannot comply with the TSS because of their type, size or poor manoeuvring characteristics. The selection of size criteria to comply with the TSS has been a matter of discussion. This paper presents the results of a real-time simulation study investigating the manoeuvring performance of large tankers in the Bosporus. The study was conducted with a simulator capable of subjecting a given hull form to any combination of environmental conditions, i.e. wind, current and wave drift forces. The results indicate that, when realistic environmental conditions are taken into account, the size of ships that can navigate safely in compliance with the traffic separation lanes is limited.
This paper presents flexible numerical procedures for fairing hull form design curves which form the three dimensional ship body. The traditional solution to the problem of fairing ship hull forms is to reduce the problem to simultaneous fairing of two dimensional curves on three orthogonal planes, called the section lines, waterlines and buttock lines. However, this process requires excessive time and experienced personnel. Fairing procedures employed in most Computer Aided Ship Design (CASD) software are computerised versions of the manual method and hence have similar drawbacks. The approach adopted in this study is based on approximation of ship lines by B‐splines that are already fair. It is shown that the degree of fairness can be improved by increasing the order of the B‐spline; however, this may result in excessive deviations from the original offset points. A balance between closeness and fairness can be identified by successive applications of B‐spline to original offsets in an iterative manner. Alternatively, B‐spline fitting instead of B‐spline approximation can be applied in order to minimize the deviation from original offset points. For ship hull forms, in order to obtain three dimensional fairness, two dimensional ship lines on three orthogonal planes need to be faired simultaneously The fairing process is first applied to waterlines and the modified offsets are transferred to other planes. The iterative process is repeated until specified degree of fairness is achieved. This procedure is applied for fairing the lines of a distorted mathematical hull form and the parent hull of a high speed hull form series. The results indicate that these procedures are particularly useful for high speed displacement hull forms and can be used as practical design tools in the early stages of ship design.
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