FLOODSTAND

The flooding of a damaged ship is a time-dependent process that is significantly affected by the non-watertight structures inside the watertight compartments. For certain ship types, like passenger ships, such structures form a complex internal subdivision. Time-domain simulation is the most realistic approach to calculate progressive flooding in damage stability analyses, but it is necessary to use a simplified method for modelling the leakage and possible collapse of the non-watertight structures. This paper presents unique full-scale tests and advanced finite element analyses, conducted to determine the leakage and collapse characteristics of various typical non-watertight structures, when subjected to water pressure. The obtained results are carefully analysed, and a simplified method for modelling the leakage of closed doors for time-domain flooding simulation is presented. For all tested doors leakage started practically immediately when immersed. Various deformation and collapse mechanisms were observed, and often the leakage increased with larger pressure head due to the deformation of the door. The collapse pressure heads varied between 1.0 m and 3.5 m; the cold room door having the largest value. Guideline values for typical non-watertight doors were derived based on the obtained results.

Progressive flooding inside a damaged ship can seriously endanger the stability. Level sensors can be used to detect the flooding and based on this data the breach can be estimated. For decision support the prediction of flooding extent and intermediate phases is necessary. For this purpose a new simplified but still reasonable accurate flooding prediction method has been developed. Details of this algorithm and some test cases and comparisons to experimental data and time-accurate flooding simulation results are presented. The application of the developed prediction method in decision support is also discussed.

The time dependence of survivability of ROPAX vessels, when sustaining side collision damage in waves, is investigated herein by use of numerical simulations of ship motion and flooding. Conducted research confirms that ROPAX ships characteristically capsize fast, when sustaining damage leading to capsizing. A probabilistic analysis of the survive time after collision damage reveals that even for the most generic damage conditions assumed, the survival time in the case of capsizing remains short, which is characteristic of this type of ship design, disposing the typically large undivided deck to be subject to flooding in higher waves. In a case study, the unconditional survivability in waves, corresponding to survival s-factor of SOLAS regulations, is alternatively assessed with numerical simulations. The estimated survivability proves to be time independent in terms of practical implications. Observed deviations between current SOLAS formulation and simulations, suggest the employment of comprehensive simulation methods when more reliable estimations and assessments of survivability are required.