Effect of Bow Shape on Deck Wetness in Head Seas

摘要

Experiments to examine the deck wetness process and to determine the effect of above water bow form on deck wetness in head seas were conducted in the 380 ft Towing Tank of the United States Naval Academy. A systematic series of bow forms, which flare and overhang were varied, was tested on a model of the FFG7 frigate at one speed in irregular head waves corresponding to commonly occurring conditions in the North Atlantic in winter. It was found that above water bow form had remarkably little effect on relative motions or deck wetness and the greatest incidence of deck wetness occurred with one of the extremely flared forms. A new method of calculating the probability of deck wetness is proposed and verified. The calculation explains why the bows tested all had a similar performance and suggests that this is about the best that could be achieved at the chosen freeboard. Application of the calculation to a wider range of bow designs shows that a similar, near optimum, performance should be achieved providing in the flare and overhang are given certain minimum values. Excessive flare and overhang will not ensure improved performance.