2 The Model 



Model-Prototype Scale Relationships 



Tests were conducted at a geometrically undistorted scale of 1:36, model to 

 prototype. Scale selection was based on the sizes of model armor available 

 compared with the estimated size of prototype armor required for stability, 

 minimization of wave transmission scale effects, preclusion of stability scale 

 effects (Hudson 1975), and capabilities of the available wave tank. Based on 

 Froude's model law (Stevens 1942) and the linear scale of 1:36, the following 

 model -prototype relations were derived. Dimensions are in terms of length 

 (L) and time (7). 



Characteristic 



Dimension 



Model-Prototype 

 Scale Relation 



Length 



L 



L r = 1:36 



Area 



L* 



A f = L r 2 = 1:1,296 



Volume 



L 3 



V, = L 3 = 1 :46,656 



Time 



T 



T, = £, 1/2 = 1 :6.0 



The specific weight of water used in model tests was assumed to be the 

 same as the prototype and equal to 62.4 pcf. Also, specific weights of model 

 breakwater construction materials were the same as their prototype 

 counterparts. Thus, the weight ratio of individual stones was the same as the 

 volume ratio, i.e., 1:46,656. 



In a hydraulic model investigation of this type, gravitational forces 

 predominate (Freudian model law), except when energy transmission through 

 the breakwater is considered (Keulegan 1973, Le Mehaute 1965). If the core 

 material was geometrically scaled according to Froudian model relationships, 

 internal Reynolds numbers would be too low, and too much energy would be 

 dissipated. Therefore, for all plans tested, the core stone and W/10 stone 

 were geometrically oversized to aid in reproducing wave energy transmission. 



Chapter 2 The Model 



