(4) The case of irregular waves. Laboratory tests with a wide 

 variety of spectral shapes suggest that there is little difference 

 in the transmission coefficient from one spectral type to another. 

 The overall transmission coefficient, Ky, is approximately the 

 same for a monochromatic test as for an equivalent irregular wave 

 test with the period of peak energy density, Tp , and mean incident 

 wave height, H, used to characterize the irregular wave conditions. 

 Figure 37 shows observed and predicted transmission coefficients for 

 a rubble-mound breakwater tested with monochromatic and irregular 

 waves. The ability of the computer program MADSEN to predict trans- 

 mission coefficients for irregular waves is at the same level as for 

 monochromatic waves for the conditions tested. 



^ B = 60cm^^ 0.61 5 ds/h 5 0.91 



, ;„Vsiope J- ^^S'^P^c) 0.002 5 d/gl^- 0.016 



^^^- "•^^^^'^ © ^^^^>v^ X^l on 15 Fronting Slope 0.00004 5 H/gT^ 5 0.0 1 3 



0.5 



BW16 



B/h = 1.82, C = 0.31 

 = 0.692, b = 0.504 



1.0 

 0.9 

 0.8 



oo <a>cB (5t) 



Wave Type 

 o Monochromatic 

 fl Irregular 



0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 

 Ky (observed) 



1.0 



Figure 37. Observed and predicted transmission coefficients for BW16. 



49 



