I.ZO 



H/L = 



1 I 

 004 



1 1 1 



1 1 





o 1.00 













— ' 







PT-2 at 



D/d= 14 





o 



o 



01 0,80 







/^^ ^^-^PT- 1 



al D/d=022 





o 













E 0.60 













o 













£ 0.40 

 en 













I 













> 0,20 

 o 



5 





1 



1 1 1 



i i 





1,50 200 2.50 3.00 



Relative Wavelength (L/B) 



3,50 4.00 



Figure 40. Comparison of PT-1 and PT-2 wave 

 attenuation (d = 4.7 m) . 



c. Goodyear Breakwater . Giles and Sorensen (1978) obtained prototype- 

 scale wave transmission data for the Goodyear floating tire breakwater using 

 the large wave tank at CERC. Data for the 6-module-wide Goodyear breakwater 

 are plotted in Figures 41 and 42, along with the wave transmission curve for 

 the PT-2 module. Both breakwaters are constructed from automobile tires and 

 have a beam of 12.2 meters which is equivalent to B/D = 18.5. For the lower 

 water depth case considered in Figure 42, it is evident that the PT-2 break- 

 water is substantially more effective than a Goodyear breakwater of equal 

 size. At the larger water depth considered in Figure 41, the PT-2 breakwater 

 is still superior but not as much so as at the lower water depth. 



From extensive small-scale experiments by Harms (1979a, 1979b), the 

 influence of water depth is found not to be of practical importance for the 

 Goodyear breakwater, at least for values of D/d less than 0.4, although 

 C^ clearly decreases as D/d increases. How significant the influence of 

 D/d is for the full-scale Goodyear breakwater (Figs. 41 and 42) is shown in 

 Figure 43 where the data for D/d = 0.16 and 0.33 may be compared while keep- 

 ing L/B, H/L, and B/d constant; the difference in C t is typically less 

 than 0.1 (the C t values near L/B = 2 are probably false). Small-scale and 

 prototype-scale data are therefore in agreement and the single Goodyear wave 

 transmission curve of Figure 44 (Harms, 1979a) may be used for most practical 

 applications as long as D/d does not exceed 0.4; near D/d = 0.4 the design 

 curve will be somewhat more conservative than at lower values of D/d. 



The performance of the PT-1 module is compared to that of a Goodyear 

 breakwater of equal size in Figure 44. It is apparent that the PT-Breakwater 

 provides substantially more wave protection than the Goodyear breakwater. It 



42 



