Abstract
Modelling of green water ingress into holds of an open-top containership in its preliminary design phase In this paper a method is presented of modelling the green water ingress into holds of open-top containership, which can be useful in the preliminary ship design phase. As a result of the research a mathematical formula which makes it possible to determine a minimum freeboard height with a view of as- low- as- possible occurrence rate of green water ingress into holds at given ship design parameters, was obtained. The research was carried out under assumption of constant ship hull dimensions. The design formula was elaborated by using a method based on a goal-oriented conceptual approach to formulation of design criteria, proposed by IMO. On the basis of the concept a deterministic scenario describing operational conditions of the ship in question, was assumed, and for the conditions the research was performed.
Highlights
The traditional design process of ships develops in an iterative way in accordance with the so-called Evans or Andrews-Evans spiral where design characteristics are evolutionarily improved by making successive trial – error steps
In order to increase degree of accuracy of the preliminary design phase the designers must be fitted with appropriate tools for precise prediction of selected design characteristics in this design phase, based on ship’s main design parameters
In this paper the influence was presented of ship hull form parameters on water ingress into the holds, that made it possible the formula for elaborating the minimum value of freeboard height for open-top containership
Summary
The traditional design process of ships develops in an iterative way in accordance with the so-called Evans or Andrews-Evans spiral where design characteristics are evolutionarily improved by making successive trial – error steps. As the deterministic scenario (operational conditions) was assumed the following conditions which comply with the IMO recommendations concerning execution of model tests on opentop containerships [6] were selected: the recommended significant wave height Hs = 8.5 m wave periods taken every 30 s within the range from 3.5 s to 17 s the ship motion parameters most unfavourable with a view of green water entering the deck: (the ship speed v and wave encounter angle β) full load conditions (i.e. maximum ship draught) the investigations were performed for the point on the deck, in which the greatest green water ingress onto the deck occurs (bow part in vicinity of 1st hold). In order to determine influence of initial transverse metacentric height on frequency of water ingress into the holds calculations were performed by assuming ship motion parameters and wave parameters in compliance with the assumed deterministic scenario. After transforming Eq (23) a design guideline was achieved for determining the minimum freeboard height, FB, in assumed operational conditions and for an arbitrary value of the hourly occurrence rate of water ingress into the holds, nz:
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