Ochi 



By using these values and Eq. (23) the time interval between two severe 

 slams was evaluated, and the results are shown in Fig. 17. Included also in the 

 figure is the experimentally obtained histogram. On the basis of the agreement 

 between experimental and theoretical results, it is concluded that the time in- 

 terval between two severe slams follows a truncated gamma probability law. 



Fig. 17 - Sample histogram and the 

 predicted probability density function 

 for time interval between two severe 

 slams (severe Sea State 7, ship speed 

 10 knots, light draft) 



APPLICATION OF THE PREDICTION METHOD TO THE 

 DECK WETNESS PROBLEM 



Prediction of Probability of Occurrence of Deck Wetness 



The problem of probability of occurrence of deck wetness due to shipping of 

 green water can be treated in a manner similar to that for slamming. However, 

 two differences in the treatment of these phenomena must be considered. These 

 are: (1) The bow emergence and threshold velocity are the required conditions 

 leading to slamming, while the bow submergence is the condition leading to deck 

 wetness. (2) The reference location along the ship length for which the proba- 

 bility should be considered is 0.1 L aft of the forward perpendicular for slam- 

 ming, and the forward perpendicular for deck wetness. Since deck wetness is 

 caused by the green water flowing over the deck from the top of the stem, it is 

 proper to consider the forward perpendicular as a reference point. Justification 

 for selection of the reference point of 0.1 L aft of the forward perpendicular for 

 slamming is given in Ref. 4. With the above two considerations, the probability 

 of occurrence of deck wetness can be obtained from Eq. (5), by substituting D 

 (freeboard at the forward perpendicular) for H (draft at Station 2), and by letting 

 r^ = 0. That is, 



572 



