Development on the Practical Measuring System of Directional Spectra of Ocean Waves.

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A developmental research on the practical measuring system of directional spectra of ocean waves was carried out by measurement of the artificial short crested irregular waves generated in the long experimental tank of Yokohama National University. Those short crested irregular waves were exactly given the specified directional spectra by the newly developed multi segmented wave generator.Consequently a new complete system which has following specialties was developed.1. A new wave probe for multi points using laser beams that projected vertically from underwater was invented. Laser spots on the wave surface are taken by a TV camera from diagonally upward direction and recorded by the video tape recorder. Recorded video is processed, read out by digital and converted to surface elevation of multi points by the digital calculation.This new laser wave probe has great merits, viz. non contact measurement,highprecision,high frequency response,small size etc.2. Analysis of directional spectra is Performed in short time by the personal computer system with high speed plotter printers. Directional spectra are calculated by the adaptation of the maximum likclihood method under the fine resolution of wave frequency and direction. Hard copies of various figures of the measured directional spectra can get in almost real time at that measuring place.3. It is not so difficult to make a new measuring system for actual ocean by the development of this new system.