4. Experimental Evaluation of Proposed Model Law of Noda . 



The last part of this study was modeling beach profiles obtained 

 independently by CERC and not available to Tetra Tech, Incorporated, at 

 the time of testing. A summary of test conditions for the CERC unpub- 

 lished profiles is given in Table 6. 



An investigation of the implications of Noda's model law (eqs. 17 and 

 18) indicated a requirement for a modeling material having a submerged 

 specific weight in the range y' = 0.3 to 0.8 with a size in the range of 

 DcQ = 0.6 to 1.5 millimeters for the most useful modeling scale in the 

 available wave flume. 



In practice, this particular submerged specific weight range was 

 awkward. The materials available were "loaded" PVC (y' = 0.3 to 0.4), 

 rocklite (a patented ceramic sand, y' = 0.3), pumice (y' = 0.6 to 1.2), 

 coal (y' = 0.3), anthracite (y' = 0.3 to 0.5) and various miscellaneous 

 substances like ground walnut shells and ground apricot shells. Materials 

 chosen for this study were pumice, PVC, and rocklite. Unfortunately, each 

 of these materials presents some problems. 



PVC is used commercially in "granular" form, normally a size of 2 to 

 4 millimeters. Several hundred pounds were special-ordered in "pulverized' 

 form with a median diameter of 0.6 millimeter after washing out the dust. 

 However, at such sizes the surface-tension problem was insurmountable. 

 After several weeks of soaking and treatment with detergent the material 

 formed a beach, but even the slightest wave action would "float" the 

 material in large masses. 



Pumice appeared to offer many advantages after the dust was well 

 washed out and its behavior in water created no problem other than a 

 slight milky cloudiness. However, pumice abraded under handling and its 

 density was difficult to determine. The dry specific weight of pumice is 

 about 1.6; different qualities are available with higher specific weights 

 of 1.8 to slightly over 2. The grains definitely soak up water and prob- 

 ably behave as if they have a higher effective specific weight, but this 

 effect is unknown. 



Rocklite appeared to have several practical advantages. It is rela- 

 tively cheap, and does not dirty the water too badly. Grain sizes larger 

 than 2 to 3 millimeters may include air pockets, but this was not a prob- 

 lem during tests which used a "rocklite sand" having a median diameter 

 of 1.2 millimeters. 



Rocklite and pumice were used for the model evaluation tests. In 

 practice, the rocklite was the most suitable material for modeling the 

 0.22-millimeter sand; pumice was the most suitable for modeling the 0.46- 

 millimeter sand. 



A summary of the model scale-ratio computations for rocklite, PVC, 

 and pumice versus sand of 0.22- and 0.46-millimeter diameter, and a set 

 of scale ratios for ground glass of 0.3 millimeter versus 0.6 millimeter 



