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Title: Non-Gaussian random wave simulation by two-dimensional fourier transform and linear oscillator response to Morison force
Authors: Zheng, X.Y.
Moan, T.
Quek, S.T. 
Keywords: Morison force
Two-dimensional fast Fourier transform (FFT)
Wave nonlinearity
Issue Date: Nov-2007
Citation: Zheng, X.Y., Moan, T., Quek, S.T. (2007-11). Non-Gaussian random wave simulation by two-dimensional fourier transform and linear oscillator response to Morison force. Journal of Offshore Mechanics and Arctic Engineering 129 (4) : 327-334. ScholarBank@NUS Repository.
Abstract: The one-dimensional fast Fourier transform (FFT) has been applied extensively to simulate Gaussian random wave elevations and water particle kinematics. The actual sea elevations/kinematics exhibit non-Gaussian characteristics that can be represented mathematically by a second-order random wave theory. The elevations/kinematics formulations contain frequency sum and difference terms that usually lead to expensive time-domain dynamic analyses of offshore structural responses. This study aims at a direct and efficient two-dimensional FFT algorithm for simulating the frequency sum terms. For the frequency-difference terms, inverse FFT and forward FFT are implemented, respectively, across the two dimensions of the wave interaction matrix. Given specified wave conditions, the statistics of simulated elevations/kinematics compare well with not only the empirical fits but also the analytical solutions based on a modified eigenvalue/eigenvector approach, while the computational effort of simulation is very economical. In addition, the stochastic analyses in both time domain and frequency domain show that, attributable to the second-order nonlinear wave effects, the near-surface Morison force and induced linear oscillator response are more non-Gaussian than those subjected to Gaussian random waves. Copyright © 2007 by ASME.
Source Title: Journal of Offshore Mechanics and Arctic Engineering
ISSN: 08927219
DOI: 10.1115/1.2783888
Appears in Collections:Staff Publications

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