l.U 







b/D 



0.8 



// 



\\\ 



0.0 



0.5 



1.0 





/'/ 



\\\ 





0.6 



/// 





- 





/'/ 



X A\ 





0.4 



" VI 



^\> 







^V 





0.2 



^^^ 



" 



0.0 



»! 1 1 



i i i i 



1 I 



0.2 0.4 



1.6 1.1 



2.0 



0.6 0.8 1.0 1.2 1.4 

 Structure Draft, D/L 



Figure 14. Effect of depth of mooring on coefficient of transmission for 

 floating breakwater, W = 0, k/pgL = 1 (after Stiassnie, 1980). 



Figure 



0.2 0.4 



1.4 1.6 1.8 2.0 



0.6 0.8 1.0 1.2 

 Structure Draft, D/L 

 Effect of depth of mooring on mooring force for floating 

 breakwater, W = 0, k/pgL = 1 (after Stiassnie, 1980). 



c. Model by Yamamoto, Yoshida, and Ijima . The two-dimensional problem of 

 wave transformation past, and motions of, moored floating objects has been 

 solved numerically by Yamamoto and Yoshida (1979), Yamamoto, Yoshida, and 

 Ijima (1980), and Yamamoto (1981). They solved this boundary value problem by 

 direct use of Green's identity formula for a potential function. The cross- 

 sectional shape of the floating object, the bottom configuration, and the 

 mooring arrangements may all be arbitrary. For a given incident wave, the 

 three modes of body motion, the wave system, and mooring forces are all solved 

 at the same time. A laboratory experiment was conducted to verify the theory. 

 Generally, good agreement between the theory and experiments was obtained as 

 long as the viscous damping due to flow separation was small. This numerical 

 study indicates that a conventional slack mooring worsens wave attenuation by 

 a floating breakwater; a properly arranged elastic mooring can considerably 

 improve attenuation characteristics. 



44 



