♦j 0.9 





«K» 



* 















I 



k\ 



















X 



^><l 



^>j 

















~ i 















_ 



-Plan 1 (V 



'idth = 12 

 Width = I! 

 fidth = 16 



ft) 

 ft) 

 ft) 



- 



---o 



-Plan 1A 

 -Plan 2 (l 



0.1 



0.7 



0.2 0.3 0.4 0.5 0.8 



Ratio of Breakwater Width-to-Wavelength, W/L 



COEFFICIENT OF TRANSMISSION (C t ) 

 note: numbers beside data po. N ts VERSUS RELATIVE WIDTH (W/L) 



INDICATE THAT THE NUMBER TWO-DIM ENSI ONAL TESTS 



OP DATA PO'NTS EXCEEDS ONE. 



Figure 24. Effect of relative breakwater width, W/L, on coefficient of 

 transmission, C t , for single-pontoon floating breakwater eval- 

 uated in two-dimensional wave flume for potential application at 

 Olympia Harbor, Washington (after Carver, 1979). 



Carver (1979) observed that the plans 1 and 1A test results afforded some 

 interesting comparisons. Based solely on the physical dimensions of the 

 structure, it is probably reasonable to assume that for the range of wave 

 conditions tested, plan 1A exhibited a slight increase in performance relative 

 to plan 1. Actually, plan 1A exhibited slightly higher transmitted values for 

 the 2.5-second wave period, slightly lower values for the 3.0-second wave 

 period, and almost the same values for the 3.5-second wave period. The 

 dynamic response of plan 1A was significantly different from Plan 1. A 

 decrease in roll and an increase in heave was observed for all wave condi- 

 tions; consequently, the mechanism of wave transmission was fundamentally 

 different, thus accounting for the variations in transmitted wave heights. 

 Based on these observations (Carver, 1979), the decrease seems to result from 

 wave components generated by heave and sway motions being almost 180° out of 

 phase and tending to cancel each other. Since plans 1 and 2 were both single- 

 pontoon floats with widths of 12 and 16 feet, respectively , plan 2 was expected 

 to generally yield somewhat lower transmitted wave heights than plan 1. There 

 was, indeed, a consistent trend of plan 2 exhibiting an increase in perform- 

 ance relative to plan 1 for W/L values greater than about 0.3; however, this 

 improved performance was not discernible at smaller values of W/L. 



56 



