The above discussions o£ wave generators show that, except for the 

 flap generator, even the simple theory is accurate enough for determining 

 wave heights for the design of new generators, in selecting linear scales 

 for proposed models, and as a basis for correlating test results to reduce 

 the work required to calibrate a generator. However, for model studies of 

 coastal structures, the wave generator should be calibrated as accurately 

 as possible, over the ranges of the variables used in the testing program, 

 and under the conditions that exist in the wave flume. The calibration 

 curves obtained should be checked at regular intervals. 



The horsepower required to operate a wave generator must be suffi- 

 cient to supply the power necessary for generation of the waves, includ- 

 ing the waves generated in the rear of the generator, leakage around the 

 edges of the generator, and the inertia and friction forces of the gen- 

 erator assembly. The required wave power as determined from wave theory 

 is 



,., Group Velocity x Wave Energy 



Wave power = ^- \ ; 2=^ 



Wavelength 



from which the wave horesepower per foot of generator is 



(' 47rd \ 



where Y^^ is specific weight of water, V is the wave velocity 



V - (^f^ tanh -^ j C6-25) 



and k is a coefficient that is a function of the generator shape, 

 k = 2 for the piston, flap, and cylindrical plunger, less than 2 for 

 the prismatic plunger, depending on the value of b, and can be made 

 less than about 1.5 by inclining the bottom part b of the plunger 

 toward the wave direction, and placing a fixed vertical plate within 

 about 0.5 inch of the rear face of the plunger. Experiments conducted 

 at CERC (Madsen, 1970) indicate that leakage around the edges of a gen- 

 erator can cause a considerable reduction in wave height if care is not 

 taken to reduce leakage to a minimum. However, if the use of zero- 

 linkage gaskets are attempted, the friction factor may increase the 

 horsepower requirements appreciably. Tlius, an acceptable compromise 

 must be determined. The horsepower required to operate the wave gen- 

 erator, excluding that i-equired for the wave power alone (eq. 6-24] , is 

 difficult to calculate accurately, varies considerably with the type of 

 generator, and is usually estimated from previous experience. The ratio 

 of the motor horsepower (mhp) to the wave horsepower (whp) varies with 

 the inertia of the generator, wave period, friction, leakage, and ability 

 of the machine to generate a pure sinusoidal wave. The peak power re- 

 quired can be reduced considerably by an inertia (fly) wheel. Typical 



350 



