International Shipbuilding Progress

A potential based panel method is presented to estimate the wave-making characteristics of multi-hull craft. In order to simulate the lifting potential flow around the sub-hulls, the method adopts mixed source/doublet distributions on the sub-hulls and their wake surface, while sources are distributed on the main hull and the free surface. In this way, the asymmetric flow characteristics of the sub-hull are properly simulated, i.e., a Kutta condition is satisfied at the trailing edge of the sub-hull. Comparison is made between the numerical and model experimental measurements, and a good correlation has been found. The wave-making characteristics and pressure distributions on the sub-hull predicted by the present method can differ from those based on a distribution of sources alone, especially the pressure distributions at the stern of the sub-hulls.

Some vessel types, such as warships and motor yachts, are often required to operate efficiently at two different speed zones: low speed cruise; and high-speed sprint. In the past, a single optimised hull form has been developed, with a balance between the different roles, based on the requirement set and on the operations envisaged.

This paper reports on the results from an investigation into the possible advantages of a ship with a reconfigurable hull form, allowing optimisation for each of the two different speeds. This follows on from earlier work (Int. J. Maritime Engg 148) which demonstrated possible improvements in operational efficiency.

The two main improvements demonstrated in the earlier work were due to stern shape reconfiguration and change in propulsor type from waterjet propulsion to an azimuthing thruster. The current work focuses on these areas in more detail.

Resistance experiments were conducted with and without a stern extension at three displacements to determine the influence of increasing the displacement due to the additional mass required for the reconfiguration.

The results were applied to a test case of a Fast Offshore Patrol Vessel, and it was demonstrated that considerable savings in fuel could be possible, depending on the operational profile, and the additional mass required for the reconfiguration.

This paper considers modelling of hydroelasticity in water impacts of ship-hull bottom-panels by use of explicit finite element methods. The finite element analysis is based on a multi-material arbitrary Lagrangian–Eulerian formulation and a penalty contact algorithm. This modelling technique enables the modelling of the instantaneous fluid-structure interaction. The FE-modelling of elastic panel-water impacts is evaluated by a convergence study and by comparison with experiments. Hydroelastic effects on the panel response are systematically studied for different impact velocities, boundary conditions and structural mass. It is concluded that hydroelastic effects can result in a significant reduction of the structural response for certain combinations of panel deadrise, impact velocity and boundary conditions. Inertia effects are shown to be dominated by added water mass. The present study is compared with other published work concerning hydroelasticity in panel-water impacts.

The paper explains the elements of a holistic framework on design for ship safety addressing in particular an effective balance among risk, cost and performance criteria. Ship safety can be influenced by several factors over time and it is apparent that all such factors should be taken into account, in a balanced and systematic manner during the life-cycle of the vessel, in order to reach an acceptable, viable solution optimally. Particular attention is paid on the balance of conflicting risks and costs deriving from different hazards, as well as in techniques used for the estimation of risks levels based on first-principles tools. A case study is presented to address the application of the developed framework, aiming to provide insight in the proposed procedure as well as to demonstrate its potential for wider application.

We describe here an extensive set of experiments on a series of five simplified transom-stern ship models. The local wave elevation was measured using surface transducers on the two sides of the model at the transom, as well as at the center of the transom.

This data has been analyzed and a new regression formula for the progressive ventilation of the transom, as a function of the transom-draft Froude number has been developed. These formulas take into account both the transom beam-to-draft ratio and the transom-draft Reynolds number. There is now strong evidence that the transom-draft Reynolds number plays a much lesser rôle in this phenomenon than previously thought.

Using these new formulas, one can now predict the resistance components with greater confidence. Hence, the resistance of a high-speed vessel with a transom stern can be estimated accurately over the entire speed range.

This paper reviews cavitation research on ship propellers performed in the recent past in MARIN's Depressurized Towing Tank and cavitation tunnels. Cases are presented through which advances have been made possible in the design of propellers and ships, and unresolved issues are discussed that form the challenges of future research. Our focus is on inception, hull-pressure fluctuations, and erosion on propeller blades and rudders.