ON THE STABILITY OF FAST FERRY IN DAMAGE SCENARIOS

The ro-ro ships are characterized by a large garage compartment extending from stern to bow. Damage conditions, heavy weather and large floodable spaces could create serious accidents, with the loss of life and goods at sea, both for conventional ferries and fast ferries. The occurred accidents showed the need of a more accurate approach to the damaged ship stability in waves, also in head sea and following sea conditions, because of the great movements of water on the car deck. With this aim a tool for analysing the ship response in wave with damaged compartments has been developed and applied on a typical fast ferry. The ship dynamic is simulated in time domain, including non-linear effects, taking into account critical scenarios on the damaged ship. The applications regard ship grounding, assuming head sea, modelled by regular wave. In addition to that, also the particularly critical condition of a transversal wind heeling moment has been applied to compute non symmetrical behaviour. Moreover the stability problems arising from the presence of trapped water in the garage compartment are investigated assuming the same environmental scenarios.

Assessment of wind heeling lever determined through CFD against the current naval stability standards

Naval stability standards consider the impact of a number of different external factors, one of which is the effect of heeling caused by wind. With relatively large superstructures the wind heeling moment can be relatively significant but despite its potential impact, at present the calculation to determine the wind heeling moment is relatively simplistic. With increasing fidelity within computational tools, in particular Computational Fluid Dynamics (CFD), it questions whether the current standards are still considered fit for purpose or whether a more time consuming but comprehensive analysis should be used. This paper discusses work conducted by QinetiQ on behalf of the UK MoD, to explore this area. The work firstly benchmarks wind heeling moment derived by different CFD methods against existing model wind tunnel test results for a heeled patrol boat. The benchmarking compares the level of accuracy of the numerical tools and explores the impact of changing different parameters within the analysis. Following the benchmarking at model scale, CFD is used to calculate the wind heeling force on two ships at full scale. The two selected ships represent very different types of hullform and ship particulars. The results from the CFD analysis are then compared to the results determined using current naval standard wind heeling criteria. This paper discusses the different CFD methodology applied, the results from the benchmarking, the comparison between the CFD results and those determined by applying the current naval standard criteria and the implications on the applicability of a CFD analysis rather than the current criteria.

Steady performance prediction of a heeled planing boat in calm water using asymmetric 2D+T model

This article presents a simple mathematical model for predicting the running attitude of warped planing boats fixed in a heel angle and free to trim and sinkage. The proposed model is based on asymmetric 2D+T theory utilizing a pressure equation which is previously introduced in the literature to compute the hydrodynamic force acting on a heeled planing hull. Integration of pressure distribution on the asymmetric wedge sections enables the suggested model to compute trim angle, center of gravity rise, resistance, and heeling moment acting on the heeled planing boat in calm water. The hydrostatic force in addition to two drag forces acting on the pressure area and spray area are also taken into account. Finally, a computational algorithm is introduced to find the running attitude of the heeled planing boats. The validity of the proposed model is examined by comparing the obtained running attitudes for two planing hulls series with zero heel angle and computed lift force and heeling moment of a heeled planing boat against available experimental data. Based on the comparisons, favorable accuracy is observed for both symmetrical and asymmetrical conditions. Moreover, it is shown that existence of a heel angle can lead to a decrease in trim angle and resistance, while it intensifies the center of gravity rise of planing boats. It is also observed that as the beam Froude number increases, the heeling moment of the heeled boat reduces.

Heeling Moment Acting on a River Cruiser in Manoeuvring Motion

By using fully theoretical method the heeling moment due to centrifugal forces has been determined for a small river cruiser in turning manoeuvre. The authors applied CFD software for determination of hull hydrodynamic forces, and open water characteristics of ducted propeller for estimation of thrust of rudder-propellers. Numerical integration of equations of 3DOF motion was used for prediction of ship trajectory and time histories of velocities, forces and heeling moment.

MODEL-BASED INVESTIGATIONS ON DYNAMIC SHIP HEELS IN RELATION TO MARITIME TRANSPORT SAFETY

The paper has been presented criteria of similarity between of liquid motion. Results of initial research on air flow’s dynamic impact on a ship model of 888 project type are presented in the elaboration as well. The research has been executed at a test stand located in the Polish Naval Academy. The ship model of 888 project type has been an object of the tests. Results of executed measurements have been compared with theoretical calculations for an angle of dynamic heel. Input parameters for the tests and calculations have been defined in accordance with recommendations of Polish Register of Shipping (PRS) and IMO (IMO Instruments). Determination of a heeling moment by wind operation has been a key issue.

On the Stability of Fast Ferry in Damage Scenarios

"The ro-ro ships are characterized by a large garage compartment extending from stern to bow. Damage conditions, heavy weather and large floodable spaces could create serious accidents, with the loss of life and goods at sea, both for conventional ferries and fast ferries. The occurred accidents showed the need of a more accurate approach to the damaged ship stability in waves, also in head sea and following sea conditions, because of the great movements of water on the car deck. With this aim a tool for analysing the ship response in wave with damaged compartments has been developed and applied on a typical fast ferry. The ship dynamic is simulated in time domain, including non-linear effects, taking into account critical scenarios on the damaged ship. The applications regard ship grounding, assuming head sea, modelled by regular wave. In addition to that, also the particularly critical condition of a transversal wind heeling moment has been applied to compute non symmetrical behaviour. Moreover the stability problems arising from the presence of trapped water in the garage compartment are investigated assuming the same environmental scenarios."