Damage survivability of passenger ships in a seaway
This thesis addresses the formulation and assessment of the damage survivability of passenger/RO-RO vessels from a fundamental point of view, whilst accounting for water ingress and taking fully into consideration vessel and flood water dynamics. Following the mathematical formulation, a numerical code was developed in the time domain capable of predicting the dynamic behaviour of the damaged vessel in a realistic environment. The developed model describes a free drifting vessel undergoing extreme motions in six degrees-of-freedom under the action of wind, current and waves of arbitrary direction whilst subjected to progressive flooding. The position and attitude of the vessel are updated continuously in time and consequently all the terms in the vessel/flood water systems. A semi-analytical method is also presented, for the evaluation of the flooding rate as a function of the relative position of the water level on either side of a damage opening. This treatise begins w ith a thorough review of the available literature concerning models and methods proposed to date to assess damaged stability and survivability of passenger ships aiming to identify the strength and weaknesses of the existing theories and determine the key factors involved in the degradation of a vessel's ability to survive damage. Having validated the numerical code to the extent that confidence was gained of its ability to simulate the dynamic behaviour of the damaged vessel meaningfully and to predict her resistance to capsize with acceptable accuracy, a topdown approach was pursued, leading from a comprehensive model - including most of the critical features highlighted by the preliminary investigation - to a simplified one in which only the most relevant elements are retained if the significance of which had been demonstrated through a sensitivity analysis designed for this purpose, thus aiding in the transition of complex models to becoming useful engineering "tools". The mathematical/numerical models described in this thesis represent the most advanced treatment to date of the ability of a damaged vessel to resist capsize in a seaway. The most surprising conclusion of the investigation presented herein is that the damage survivability of a passenger/RO-RO ships can be predicted with sufficient engineering accuracy with the simplest of models, deriving from the fact that at the final stages before capsize, the "fate" of the vessel is governed by quasi-static forces.