波浪中の船のDeck Wetnessに関する長期予測

抄録

A method of predicting the short term probability of deck wetness and the long term probability of “wet-deck navigation” is presented, along with results of its application to cargo ships operating on the North Atlantic.
Relative bow motions have been evaluated theoretically for geometrically similar ships of various sizes at different headings to regular and irregular waves, based upon the linear strip theory and the linear superposition technique. According to those results, the relationship between the short term probability of deck wetness related to bow freeboard and the significant wave height of irregular sea has been determined in correlation to average wave period, heading angle and ship speed. Then, the long term probabilities of “wet-deck navigation”, where the short term probability of deck wetness will be larger than 1/10, are predicted for different seasons and for various wind forces by the aid of long term wave statistics on the North Atlantic.
The following trends of deck wetness related to bow freeboard are concluded from the predicted results :
(a) The probability of deck wetness is large in head and bow seas, and small in following, quartering and beam seas.
(b) The probability of deck wetness decreases with decrease of ship speed, but the influence of ship speed is rather small in higher speeds beyond 10 knots.
(c) A large sized ship has small probability of deck wetness.
(d) A full ship has small probability of deck wetness.
(e) The long term probability of “wet-deck navigation” is large in winter and small in summer on the North Atlantic.
(f) The long term probability of “wet-deck navigation” increases with increase of wind force on the North Atlantic, but this trend is not so remarkable in extremely heavy weather.