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The probability of capsize of purse seiners in irregular beam seas and the effect of freeboard height and metacentric height
on trapped water on the deck was investigated. The aim was to quantify a safety level that can be achieved by direct stability
assessment for this type of fishing vessel. The amount of trapped water on deck was numerically estimated using a hydraulic
flow assumption. The long-term capsizing probabilities were estimated using a piecewise linear approach together with wave
statistics from major Japanese fishing areas. The estimated safety level of capsizing probability was compared with that obtained
by the IMO weather criterion and by the water-on-deck criterion of the IMO Torremolinos Convention. Numerical results for
four typical Japanese purse seiners indicated that the effect of freeboard, on the amount of trapped water on deck, is more
important than that of the metacentric height. Besides the metacentric height and the freeboard, it was shown that the danger
of capsizing is a function of the rise of floor. The safety level obtained by the capsizing probability approach is generally
higher than that based on the IMO weather criterion. However, the water-on-deck criterion provides a higher safety level than
the capsizing probability approach for ships with a low rise of floor. 相似文献
2.
The authors have already examined a method for evaluating the capsizing probability of a ship in the dead ship condition based
on a piecewise linear approximation of the restoring arm. Here, this method is extended to ships with trapped water on deck.
This is because the stability of ships having a relatively high bulwark, such as fishing vessels, could substantially deteriorate
due to trapped water on deck. First, the mean amount of water trapped on deck was estimated as a function of the significant
wave height and the mean wave period using a model experiment in irregular beam seas. Second, the restoring arm curve with
trapped water on deck was calculated hydrostatically and then approximated with a piecewise linear curve. Third, the roll
angle was estimated using a nonlinear and uncoupled equation of absolute roll angle under stochastic wave and wind exciting
moments. The short-term and long-term capsizing probabilities were calculated for a fishing vessel operating off Kyushu. Numerical
results quantitatively demonstrated that the effect on capsizing probability of trapped water on deck cannot be ignored when
accurately evaluating the stability of fishing vessels. 相似文献
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