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E. DPG Simulation and Error 



A simple simulation program was utilized to test the 

 capabilities of the software. A directional wave-pressure field over 

 water depth h, at transducer depth s, was considered using 



J H. 



P(x,y,s;t) = yh + T Y "^ K cos (k x+k y-at) , (4.57) 

 • _! 2 p , X y J ' 



where J = number of wave trains present. Multiple wave trains of 

 different frequencies and/or directions were simulated by 

 superimposing all of the dynamic water surface elevations at (x,y,t) 

 onto the static water column, h. The pressure at those (x,y) points 

 corresponding to the five DPG diaphragm locations were generated over 

 time. (It was assumed that the five diaphragms in the center of the 

 instrument occupy the same point.) From these values, four 

 differential signals and one absolute signal were developed at At 

 intervals for a record length of NAt to simulate DPG in-situ 

 performance. Non-linear wave-wave interactions were not considered 

 in this simple model. 



The integrity of the FFT analysis was first tested by 

 simulating a single wave train at a principal frequency of the FFT. 

 Results of the analysis of the simulated record indicated acceptable 

 FFT performance since all of the energy was indeed found to be 



