不規則波中における非線形応答の極値分布の計算

概要

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According to a linear theory, the probability density function of the maxima of response whose spectrum is narrow banded can be expressed by the Rayleigh probability density function. However, this function does not reflect the asymmetrical characteristics with regard to maxima (positive amplitudes) and minima (negative amplitudes) which are seen in the experimental results. Especially in the case of relative motion (one of the most important factors in the safety operations of semi-submersibles), the linear theory tends to underestimate results relative to the experimental data. In order to obtain better results, the second order theory must be considered. Starting from the functional polynomial method, Vinje derived a method to calculate the nonlinear distribution using both time domain and frequency domain representations of the system However, he did not show the calculated results of the density or distribution. In the present work, the frequency domain method proposed by Vinje is applied to calculate the probability distribution and density of the relative motion of a semi-submersible. At first, the distribution of irregular wave elevation was calculated and compared with experimental data. After ascertaining the effectiveness of the present method. a calculation of the relative motion was carried out as the second step. The calculated results agree fairly well with the experimental results.
社団法人日本船舶海洋工学会の論文