- 6? 



concentrated at the simulated wave frequency. 



The ability to discriminate a number of different wave trains 

 was next tested. Two wave trains of frequencies within one spectral 

 bandwidth of one another and of different energy and direction were 

 superimposed upon a train of lower frequency. Analysis was carried 



oToo lb .00 2b. 00 3b. 00 4b .oo sb.oo sb.oo 



TIME (seconds ) 



FIGURE IV-5: Simulated time record of water surface 

 elevation. Case 1. H - A ft., = A6 deg., "7-98 

 sec. pd.; H=3 ft., e = 180 deg., 6.33 sec. pd.; 

 H = 4 ft. , e = 300 deg., 9.00 sec. pd. 



out for 512 sample points of 0.25 second interval. A portion of the 

 simulated time record of the water surface displacement generated 

 over each of the five sampling points of the DPG is shown in Figure 

 IV-5. The raw spectral energy distribution, or energy spectra, 

 presented in Figure IV-6, illustrates the presence of three distinct 

 frequencies well. Although the simulated lowest and highest 

 frequency waves were of the same wave height, the higher frequency 

 wave demonstrates a smaller energy spike due to the spectral leakage 

 between the lower frequency bands. The non-smoothed 7~coef f icient 



