Since only three of the four it terms in f can be held constant, 

 model-to-prototype, special scale-effect tests must be conducted over a 

 wide range of values of the Reynolds number term, Q^/v, to determine 



As in the pneumatic breakwater tests, each depth d would correspond to 

 another model, and from equation (6-17) , 



which would ensure that, for the same selected prototype conditions, 

 Hj^/X and d/X would remain constant during the scale-effect tests. 

 Also (eqs. 6- 19a and 6- 19b) 



'gl/3d\ /gl/3d' 



from which 





W-i'r"' 



Other ratios that can be derived from the above relations are, as in the 

 pneumatic breakwater tests (eqs. 6-9 and 6-20), 



m m ' ~ ' 



and 



P P \ P 



Np " (H " ("»'% ' 



For these tests, (jPq)j^ = CPa^p ^^^ water would be used for the test fluid. 

 3. Model Design . 



a. Field Data Required . In the design of hydraulic models, it is 

 important that adequate information is available about the prototype so 

 that major problems confronting the field design engineer are clearly 

 understood by the laboratory engineer. The purpose and scope of model 

 studies should be determined to the extent possible at the outset. Model 

 design and the testing program can then be better directed toward solution 

 of those parts of the overall problem that are the most critical and are 

 best suited for investigation by a hydraulic model. In addition to gen- 

 eral information about the design problems (to determine the purpose and 



333 



