Recofd wl I 



}ifferential 

 tonometer 



Lobofotofv Floor 



Measuring 

 Prob« 



Hydroufic 

 Jet 



Measuring 

 Probe 



Chonnel Bottom 



56'-6* , , 25-0", 



Differential 



Manometer Absorber. 



Meter ^''""> 



Figure 6-66. Sketch of test setup in the large channel, hydraulic 

 breakwater tests (Herbich, Ziegler, and Bowers, 1956). 



(i) Summary of Test Results . Conclusions from the tests are; 



(1) Water discharge and horsepower requirements 

 for the hydraulic breakwater are dependent on the d/A and H/A 

 ratios, the manifold jet characteristics, and the submergence of 

 the nozzles; 



(2) a single manifold system is effective for deep- 

 water waves, but its effectiveness decreases with decreasing 

 values of d/A; 



(3) power requirements increase with wave steepness 

 for high attenuation values; however, the efficiency of the sys- 

 tem, which is based on the ratio of the difference between inci- 

 dent and transmitted wave energy to the jet energy, is higher for 

 the steep waves than for the flat waves; 



(4) zero submergence of the nozzles (nozzle located 

 at the Stillwater level) is the most efficient for the range of 

 wave conditions tested; 



(5) the power requirement at the nozzles decreases 

 and the discharge increases as the jet area [jet diameter and 

 number of jets per foot of manifold) increases; however, since 

 the energy losses in the pumping and supply systems are depend- 

 ent on the discharge, these systems must be analyzed along with 

 the manifold jet system to determine the optimum jet area; and 



(6) comparative data for the hydraulic breakwaters 

 tested in the small and large wave flumes (scale ratio of 1:4.5) 

 agree quite well when compared on the basis of Froude's law for 

 d/A values between 0.56 and 0.82. 



44 



