Trans RINA, Vol 157, Part A3, Intl J Maritime Eng, Jul-Sep 2015
ON THE STABILITY OF FAST FERRY IN DAMAGE SCENARIOS (DOI No: 10.3940/rina.ijme.2015.a3.326)
M Acanfora, Aalto University, Espoo Finland, and F De Luca, Federico II, Naples Italy SUMMARY
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.
1. INTRODUCTION
The primary purpose of a ship, especially for fast ferries, is to ensure the safety of human life at sea.
The first goal of a designer is to look at the passenger safety not only through the constraint rules of regulatory bodies but also through more refined design criteria. The current stability margins are based on the rule of classification society and international regulation:
the
high speed code applies to fast vessels, set apart from Solas standards (IMO 2009).
Anyway, despite the strict rules, several accidents
involved conventional and high speed ferries. It underlines the need for a deeper approach assessing ship damage stability. In the event of damage, together with adverse weather condition, several ferries experienced loss of life and goods at sea. In particular the ro-ro ferry, in damage conditions, can be easily affected by fire or flooding
for the entire length of the garage: compartment usually has no kind of subdivision.
Ship damage stability in wave for ro-ro vessels should be investigated more in depth. Indeed, for this type of ship, the effect on stability due to water trapped in compartments characterized by high freesurface should be a sensitive problem that has to be investigated more in detail.
The potential accumulation of floodwater on the ro-ro deck space in case of damage was studied by several authors for conventional vessels (Jankowski & Laskowski
2006)
(Carette & van Walree 2011) (Acanfora & Coppola 2013) (Santos & Guedes Soares 2006), while only recently some work pointed out the need to attribute this problem also to high speed ferries (Maimun et alt. 2011). In particular, the reference paper (Maimun et alt. 2011) deals with the development of a tool for assessing damage stability in beam sea for a fast vessel.
The dynamic behaviour of a ship in damage condition is characterized by highly non-linear effects; according to
The damage simulations were carried out for a ship grounding scenario, with and without wave: in the latter case the dynamic pressure, together with the static head of water on the ship damage hole, was assumed in evaluating the flow rate during the flooding of the compartments. The ship’s behaviour with a fixed amount of water trapped on the garage deck has been also analysed.
The water within the flooded compartments has been implemented in the numerical simulation according to the lumped mass model (Manderbacka et alt. 2011).
The non-linearity due to the hull geometry and to the compartment
shape are fully taken into account: in
particular the geometrical tank properties are evaluated as a function of the water height within the compartment and implemented in the simulation by means of lookup-tables.
The ship model used for the applications represents a typical ferry operating in the “bay of Naples”.
this
The method is based on 6 degrees of freedom (6DoF) equations of motion, for the intact
ship in head or
following seas. It has also the possibility to take into account beam wind actions. The extended superstructures that characterize this type of vessels could lead to a huge wind heeling moment, responsible of non-symmetrical response of the ship during the flooding.
The main goal of this paper is to develop a numerical method, in order to evaluate the ship wave response in the presence of damaged compartments, for a fast ferry.
this, the use of time domain simulation seems to be the most suited technique to be applied to approach the problem. In the reference paper (Lee at alt. 2007) the authors developed a time domain theoretical model for the prediction of damaged ship motion and accidental flooding in waves. They also provided comparison with experimental
tests on a conventional roro-pax model.
Nevertheless the effects of the wave pressure on the flooding were not investigated.
©2015: The Royal Institution of Naval Architects
A-153
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