Mathematical models for capsizing prediction due to broaching have been developed by several researchers so far. Although some of models can predict capsizing due to broaching quantitatively, they require several captive model experiments to measure hydrodynamic forces for largely heeled condition. In our previous researches, the effects of heeling on hydrodynamic forces in severe following waves were measured up to 50 degrees of heel angle with the purpose-built experimental setup. However the previous measurement system which fixes 6 degrees of freedom of a ship model requires many extra runs to obtain the correction coefficients in heave and pitch to estimate the accurate running attitude in severe waves. Therefore we try to develop a new measurement system which fixes 4 degrees of freedom of the surge-sway-roll-yaw but allows heave and pitch motions to be free. Firstly, the comparison of the measured results between the previous measurement system and the present measurement system were conducted. Secondly, nonlinear heel-dependent hydrodynamic forces and wave-exciting forces were directly measured in severe following and quartering seas for a fishing vessel with large heel angles. Finally, comparisons between the free running model experiments and the numerical simulations with the measured nonlinear heel-dependent hydrodynamic forces were conducted to investigate their importance for broaching prediction.


The new intact stability criteria which are under development at International Maritime Organization (IMO) are required to cover a broaching phenomenon. The mathematical models for surfriding and broaching-to in following and quartering seas have been developed and well validated by comparing their numerical results with the free running model experiments by the authors [Hashimoto et al., 2004] [Umeda and Hashimoto, 2007]. However, several captive model experiments are required to measure several hydrodynamic forces acting on a largely heeled ship in severe astern seas for quantitative prediction of broaching.

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