Prediction of Ship Slamming at Sea 



^3 



I 

 o 



^2 



Threshold 

 Pressure, P« 

 12.4 PSI 



40 60 80 



Pressure in PSI 



120 



Fig. 7 - Comiparison between experimentally- 

 obtained histogram of slamming pressure 

 and predicted probability density function 

 (severe Sea State 7, ship speed 10 knots, 

 light draft) 



Comparison between theory and experiment were made for two additional 

 cases; namely for moderate and mild Sea State 7, at a 10-knot ship speed. The 

 results are shown in Figs. 8 and 9, respectively. Two histograms are shown in 

 Fig. 9; one obtained from a 30-minute observation in a mild Sea State 7, while 

 the other was obtained from a 70- minute observation in the same sea state. Al- 

 though some discrepancy between the experimental histogram and the theoretical 

 probability density function can be seen in Figs. 8 and 9, good agreement was 

 obtained between the predicted and observed averages of one-third and one-tenth 

 highest values in these two cases. 



It is noted here that a discrepancy between the experimental histogram and 

 the theoretical probability density function is noticeable in the neighborhood of 

 the threshold pressure. The discrepancy for these marginal conditions might 

 be attributed to the actual angle between wave and keel. For higher relative ve- 

 locity, however, the angle would not be expected to have a strong influence upon 

 the magnitude of impact pressure. 



It is of interest to mention that the probability density function of the im- 

 pact pressure given by Eq. (15) can also be applied for any course angle or 

 loading condition. Figure 10 shows a comparison between the experimental 



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561 



