Measuring And Analysing The Directional Spectra Of Ocean Waves

Measuring and analysing the directional spectra of ocean waves

Measuring and Analysing the Directional Spectra of Ocean Waves

COST action 714, supported by the European Commission, had the objective to promote the development of measurement techniques and the use of directional wave measurements. The action was launched in 1996, and, in the end, representatives of ten European countries (Belgium, Finland, France, Italy, Germany, The Netherlands, Norway, Portugal, Spain, United Kingdom) participated in it. Within the action a working group was created with the title Intercomparisons of Spectral Properties of Surface Waves for the purpose of improving the understanding of measurement techniques, methods of analysis, and comparisons between different instruments.

Directional Wave Measurement and Analysis

A directional wave analysis computer 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 calculated by four different methods. Results have agreed well with other wave measuring buoys as detailed in other sources. Keywords: Sea testing. (Author).