On the Directional Sea Measurement Using a Circular Array

概要

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For estimating the directional spectrum of short-crested seas Circular Array Method (CAM) is proposed. CAM is an array-dependent method, distributing wave gauges on a circle and one on the center of the circle. Through this array arrangement the Fourier coefficients of the directional distribution function can be evaluated by a simple calculation, inverse Fourier transformation of cross spectrum. But for higher orders MEM extrapolation is used. Fourier coefficients are calculated directly and distinctly with simple equation, so it is easier than other methods (e.g. MLM) to estimate the reliability of the result and to find the reason when we get an unexpected directional distribution. For a single-peak distribution the resolution of CAM is satisfactory with a skillful filter, but for complicated distribution there is a room for improvement of MEM extrapolation process. Standling wave effect caused by a reflection wall can be a serious problem for experiments in model basins and for field measurements. Application of CAM to those wave fields was studied qualitatively and quantitatively. The behavior of the interaction term was discussed relating to the distance of the array from the wall, the array size, the incident angle to the wall and so on. These discussions were confirmed by simulations.
独立行政法人海上技術安全研究所の論文
1990-11-30