ABSTRACT 



A directional wave analysis program has been 

 developed to analyze the measured directional wave data 

 from an ENDECO Wave-Track buoy. Due to the nature of the 

 buoy, the direction components must be adjusted in order 

 to apply a conventional wave slope analysis. The choice 

 of a Wave-Track buoy stems from the requirement of a 

 light-weight, easy to handle directional sensing wave 

 buoy. The results can be used to validate the directional 

 spread of wave energy produced by the Spectral Ocean Wave 

 Model (SOWM). Also, the resulting directional spread of 

 energy, as produced by the buoy, may now be used with ship 

 motions to produce ship response amplitude operator (RAO's), 

 or combined with ship RAO's to estimate ship motions. 



The equations are developed to account for buoy 

 motions in a current and in shallow water. Although 

 electronic phase shifts have been adjusted, it is still 

 necessary to develop some analytical solution to compensate 

 for hydrodynamic responses and phase shifts. 



The analyzed results include frequencies, energy 

 densities, Fourier coefficients, first and second harmonic 

 mean wave directions and root mean square (rms) spreading. 

 Also included is the directional spreading of energy calcu- 

 lated by four different methods. 



Results have agreed well with other wave measuring 

 buoys as detailed in other sources . 



ADMINISTRATIVE INFORMATION 

 This report was prepared under the sponsorship of the Naval Sea Systems 

 Command (NAVSEA) , Code 3213 Work Request Number WR91589 , the Ship Performance and 

 Hydromechanics Program funded under Program Element 625U3N and Block Number 

 ZF k3 U21 001, and the Surface Wave Spectra for Ship Design Program under Program 

 Element 62T59N and Project Number SF 59 557 695. It is identified by Work Unit 

 Numbers 1568-823 , 1500-10U, 1568-838 , and 1500-300 at David W. Taylor Naval Ship 

 Research and Development Center (DTNSRDC). 



INTRODUCTION 

 The measurement of directional waves has taken on an increased significance 

 over the last decade. The U.S. Navy has become concerned with the directional 

 spreading in addition to the energy of waves as they affect ships. It is no 

 longer sufficient to determine only the frequency distribution of the wave energy, 

 but rather the directional distribution of each component is required. 



