in equation (6-lc) has the same value in both the model and the prototype 

 for a particular form of breakwater section and a particular set of wave 

 conditions; i.e.. 



V„ 



(e,)i/2gi/2 



V,. 



(S,)fg'/^ 



(pa - "w^ ' U - "w) 



'(«4 



m/Pv 



'('c). 



m/p. 



(6-2a) 



(6-2b) 



(6-2c) 



M 



(Ma 





C6-2d) 

 (6-2e) 

 (6-2f) 



and 





m 



kJ 



«m 



A„ =A 



(6-2g) 



C6-2h) 

 (6-2i) 

 (6-2j) 

 (6-2k) 



Since stability models of rubble-mound breakwaters are designed based on 

 Froude's law and are constructed geometrically similar with undistorted 

 linear scales, all the above-listed relationships can be satisfied for a 

 particular set of test conditions except for those indicated by equation 

 (6-2 c) (Reynolds number) and equation (6-2g) (surface roughness of indi- 

 vidual armor units). The effects of surface roughness of the ordinary 

 quarrystone and concrete armor units are negligible in full-scale proto- 

 type structures, and they can be made negligible in the model by use of 

 relatively smooth-surfaced armor units. For stability models with linear 

 scales, L /L,, where the model velocities and armor-unit sizes are too 

 small, the viscous effects are accentuated and the scale effects may no 

 longer be negligible. Tests to determine the scale effects in the 



318 



