001 002 003 0-04 0-05 006 



Initial Wave Steepness, ti./L 



007 



008 



Figure 108. Effect of initial wave steepness, H^/L, and relative 

 breakwater width, L/L,, on transmission coefficient, 

 C t , for A-frame floating breakwater (after Ofuya, 1968). 



water also show that steep waves experience greater attenuation than low 

 waves. This is partly attributed to the increase in water particle velocity 

 with increase in wave steepness, and the resulting increase in loss of energy 

 due to separation of fluid at the bottom of the barrier. The increase of 

 C t with increasing steepness for certain values of L/L may be due to wave 

 generation by the oscillating breakwater. 



The effect of relative water depth, L/d, on the transmission coeffi- 

 cient, C t , is shown in Figure 109, for various values of L/d, which is 

 effectively a radius of gyration parameter. The water depths used in the 

 experiments were 1.5 and 2.5 feet. The ratio L/d, held constant for each 

 of the curves in this figure, specifies the spacing of the cylinders. The 

 wave steepness, 1L/L, varied from 0.06 to 0.07. The properties of the 

 A-frames used in Ofuya (1968) are presented in Table 6. One of the most 

 important features shown in Figure 109 is that the effectiveness of the 

 A-frame floating breakwater can be increased by increasing the cylinder 

 spacing. This process indicates an increase of the mass radii of gyration 

 of the breakwater about a lateral axis through its center of gravity. For 

 example, at a value of CL = 0/. 5, the effectiveness (length of wave which can 

 be attenuated by 50 percent) of the A-frame in wave damping can be increased 

 by a factor of about 1.7 for a threefold increase of its radius of gyration. 

 Highly significant is the fact that masses of the breakwaters under considera- 

 tion differed by only 7 percent. 



160 



