by passing some random voltage through a succession of seven identical linear networks, 

 each having a constant amplitude but prescribed phase change over the frequency range 

 (known as "all pass" networks), and then by taping each of the eight random signals. 



Considering a directional spectrum to be made up of a large number of independent 

 random wave trains, each traveling in a certain direction, an approximation to this spectrum 

 could be made with perhaps five or seven such separate oblique wave programs produced as 

 above and summed together on a composite tape. Assuming linearity of the wavemaking 

 system, the desired directional properties could be well approximated both in frequency and 

 direction through use of the techniques developed with the long-crested waves on each of 

 the oblique components. Needless to say, such an ambitious program must rest on a founda- 

 tion of experience with random unidirectional waves generated with the actuator installation, 



ACKNOWLEDGMENTS 



The author is grateful to Mr, Joseph E. Russ for his able assistance in all phases of 

 the wavemaking tests and to the staff of the Motions Analysis Section for technical advice 

 in the use of analog computing equipment. 



REFERENCES 



1, Brownell, W.F., "Two New Hydromechanics Research Facilities at the David Taylor 

 Model Basin," Paper presented before Chesapeake Section, Society of Naval Architects and 

 Marine Engineers (Dec 1962). Also David Taylor Model Basin Report 1690 (Dec 1962). 



2. Vossers, G,, "Fundamentals of the Behavior of Ships in Waves," International Ship- 

 building Progress, Vol. 6, No. 63 (Nov 1959), 



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